I think you are looking for the [Google Adwords Remarketing][1] module. Here is a quote about it (from the module's project page):

 > Adds the [Google Adwords Remarketing web statistics tracking system][2] to your website.
 >
 > NB - Google now has another (easier) method for using Remarketing tags. If your Adwords account is linked to your Google Analytics account you can enable the tag by installing the [Google Analytics][3] module and ticking a tick box under the Google Analytics Drupal admin page - see attached image.
 >
 > This tick box causes a slight alteration in the GA tag which is needed by Google Remarketing. 


  [1]: https://www.drupal.org/project/google_adwords_remarketing
  [2]: http://adwords.google.com/support/aw/bin/topic.py?hl=en&topic=27765
  [3]: https://www.drupal.org/project/google_analytics