Index: /Users/mo/Documents/workspace/HTML-FormFu-Model-DBIC/t/update/many_to_many_select.t
===================================================================
--- /Users/mo/Documents/workspace/HTML-FormFu-Model-DBIC/t/update/many_to_many_select.t	(revision 1493)
+++ /Users/mo/Documents/workspace/HTML-FormFu-Model-DBIC/t/update/many_to_many_select.t	(working copy)
@@ -1,6 +1,6 @@
 use strict;
 use warnings;
-use Test::More tests => 5;
+use Test::More tests => 13;
 
 use HTML::FormFu;
 use lib 't/lib';
@@ -39,6 +39,9 @@
     # band 3 - not used
     $schema->resultset('Band')->create({ band => 'the kinks' });
     
+    # band 4 - not used
+    $schema->resultset('Band')->create({ band => 'the hoorays' });
+    
     # band 1
     $u2->add_to_bands($band1);
 }
@@ -75,3 +78,66 @@
     is( $id[1], 3 );
 }
 
+# additive
+
+$form = HTML::FormFu->new;
+
+$form->load_config_file('t/update/many_to_many_select_additive.yml');
+
+$form->stash->{schema} = $schema;
+
+{
+    $form->process( {
+            id    => 2,
+            name  => 'Paul McCartney',
+            bands => 2,
+        } );
+
+    ok( $form->submitted_and_valid );
+
+    my $row = $schema->resultset('User')->find(2);
+
+    $form->model->update($row);
+}
+
+{
+    my $row = $schema->resultset('User')->find(2);
+    
+    is( $row->name, 'Paul McCartney' );
+
+    my @bands = $row->bands->all;
+
+    is( scalar @bands, 3 );
+
+    my @id = sort map { $_->id } @bands;
+
+    is_deeply( \@id, [qw(1 2 3)] );
+}
+
+{
+    $form->process( {
+            id    => 2,
+            name  => 'Paul McCartney',
+            bands => [qw(1 2 3 4)],
+        } );
+
+    ok( $form->submitted_and_valid );
+
+    my $row = $schema->resultset('User')->find(2);
+
+    $form->model->update($row);
+}
+
+{
+    my $row = $schema->resultset('User')->find(2);
+    
+    is( $row->name, 'Paul McCartney' );
+
+    my @bands = $row->bands->all;
+
+    is( scalar @bands, 4 );
+
+    my @id = sort map { $_->id } @bands;
+
+    is_deeply( \@id, [qw(1 2 3 4)] );
+}
\ No newline at end of file
Index: /Users/mo/Documents/workspace/HTML-FormFu-Model-DBIC/t/update/many_to_many_select_additive.yml
===================================================================
--- /Users/mo/Documents/workspace/HTML-FormFu-Model-DBIC/t/update/many_to_many_select_additive.yml	(revision 0)
+++ /Users/mo/Documents/workspace/HTML-FormFu-Model-DBIC/t/update/many_to_many_select_additive.yml	(revision 0)
@@ -0,0 +1,19 @@
+---
+auto_fieldset: 1
+
+elements:
+  - type: Hidden
+    name: id
+  
+  - type: Text
+    name: name
+  
+  - type: Select
+    name: bands
+    multiple: 1
+    model_config:
+      additive: 1
+      options_from_model: 0
+  
+  - type: Submit
+    name: submit
Index: /Users/mo/Documents/workspace/HTML-FormFu-Model-DBIC/lib/HTML/FormFu/Model/DBIC.pm
===================================================================
--- /Users/mo/Documents/workspace/HTML-FormFu-Model-DBIC/lib/HTML/FormFu/Model/DBIC.pm	(revision 1493)
+++ /Users/mo/Documents/workspace/HTML-FormFu-Model-DBIC/lib/HTML/FormFu/Model/DBIC.pm	(working copy)
@@ -61,7 +61,7 @@
     my ( $self, $base, $attrs ) = @_;
 
     $attrs = $attrs ? _compatible_attrs($attrs) : {};
-
+  
     my $form      = $base->form;
     my $resultset = _get_resultset( $base, $form, $attrs );
     my $source    = $resultset->result_source;
@@ -121,14 +121,13 @@
 
     if ( defined $schema ) {
         my $rs_name = $attrs->{resultset} || ucfirst $base->name;
-
         return $schema->resultset($rs_name);
     }
     elsif ( defined $context && defined $attrs->{model} ) {
 
         my $model = $context->model( $attrs->{model} );
         
-        if ( defined( my $rs = $attrs->{resultset} ) ) {
+        if ( defined( my $rs = $attrs->{resultset} || ucfirst $base->name ) ) {
             $model = $model->resultset( $rs );
         }
         
@@ -817,7 +816,7 @@
 
 sub _save_multi_value_fields_many_to_many {
     my ( $base, $dbic, $form, $attrs, $rels, $cols ) = @_;
-
+    
     my @fields = grep {
         ( defined $attrs->{nested_base} && defined $_->parent->nested_name )
             ? $_->parent->nested_name eq $attrs->{nested_base}
@@ -843,12 +842,13 @@
             my @values = $form->param_list($nested_name);
             my @rows;
 
-            if (@values) {
-                my $config = _compatible_config($field);
+            my $config = _compatible_config($field);
 
-                my ($pk) = $config->{default_column}
-                    || $related->result_source->primary_columns;
+            my ($pk) = $config->{default_column}
+                || $related->result_source->primary_columns;
 
+            if (@values) {
+                
                 $pk = "me.$pk" unless $pk =~ /\./;
 
                 @rows = $related->result_source->resultset->search( {
@@ -856,9 +856,23 @@
                         $pk => { -in => \@values } } )->all;
             }
 
-            my $set_method = "set_$name";
-
-            $dbic->$set_method( \@rows );
+            if($config->{additive}) {
+                
+                $pk =~ s/^.*\.//;
+                
+                my $set_method = "add_to_$name";
+                
+                my @current = map { $_->$pk } $related->all;
+                
+                foreach my $row ( @rows ) {
+                    next if grep { $_ eq $row->id } @current;
+                    $dbic->$set_method($row);
+                }
+            } else {
+                my $set_method = "set_$name";
+                
+                $dbic->$set_method( \@rows );
+            }
         }
     }
 }
@@ -1356,7 +1370,23 @@
           model_config:
             default_column: foo
 
+The default implementation will first remove all related objects and set the
+new ones (see L<http://search.cpan.org/perldoc?DBIx::Class::Relationship::Base#set_$rel>).
+If you want to add the selected objects to the current set of objects
+set C<additive> in the C<model_config>.
 
+    ---
+    element:
+        - type: Checkboxgroup
+          name: authors
+          model_config:
+            additive: 1
+            options_from_model: 0
+
+(<options_from_model> is set to C<0> because this L</options_from_model> will try to fetch
+all objects from the result class C<Authors> if C<model_config> is specified
+without a C<resultset> attribute.)
+
 =head1 COMMON ARGUMENTS
 
 The following items are supported in the optional C<config> hash-ref argument