How to integrate existing web application with Day CQ

There is already a project which is entirely JSP -- >servlets-->Database architecture.

And there are jsp/html pages.

My client wants to put some promotional content and other contents on the existing jsp/html pages.

So we are deciding to integrate Day CQ with existing web application. The reason of choosing Day CQ is that in future we can leverage more features of Day CQ on site.

So my question is --  Is it possible to put some content from CQ on any existing web application pages ?

Thanks,

Gaurav