diff --git a/app/controllers/attachments_controller.rb b/app/controllers/attachments_controller.rb
index b0e09cb..9e6dd4c 100644
--- a/app/controllers/attachments_controller.rb
+++ b/app/controllers/attachments_controller.rb
@@ -27,6 +27,8 @@ class AttachmentsController < ApplicationController
       format.html {
         if @attachment.is_diff?
           @diff = File.new(@attachment.diskfile, "rb").read
+          @diff_type = params[:type] || User.current.pref[:diff_type] || 'inline'
+          @diff_type = 'inline' unless %w(inline sbs).include?(@diff_type)
           render :action => 'diff'
         elsif @attachment.is_text? && @attachment.filesize <= Setting.file_max_size_displayed.to_i.kilobyte
           @content = File.new(@attachment.diskfile, "rb").read
diff --git a/app/views/attachments/diff.html.erb b/app/views/attachments/diff.html.erb
index 9604792..fa4e182 100644
--- a/app/views/attachments/diff.html.erb
+++ b/app/views/attachments/diff.html.erb
@@ -5,9 +5,16 @@
    <span class="author"><%= link_to_user(@attachment.author) %>, <%= format_time(@attachment.created_on) %></span></p>
 <p><%= link_to_attachment @attachment, :text => l(:button_download), :download => true -%>
    <span class="size">(<%= number_to_human_size @attachment.filesize %>)</span></p>
-
 </div>
-&nbsp;
+<p>
+<% form_tag({}, :method => 'get') do %>
+    <label><%= l(:label_view_diff) %></label>
+    <%= select_tag 'type',
+                    options_for_select(
+                      [[l(:label_diff_inline), "inline"], [l(:label_diff_side_by_side), "sbs"]], @diff_type),
+                    :onchange => "if (this.value != '') {this.form.submit()}" %>
+<% end %>
+</p>
 <%= render :partial => 'common/diff', :locals => {:diff => @diff, :diff_type => @diff_type} %>
 
 <% html_title @attachment.filename %>