Sascha,

>is here anybody with exeperience in using business object generated with mm.net 3.5 over wcf in a silverlight project?
>
>I have some trouble to find the right access how to use the wcf service with my objects in this case.

The best approach is to use MM .NET business objects in association with Silverlight RIA Services:

http://silverlight.net/getstarted/riaservices/

Best Regards,