Laser sintering gets more and more importance as a small series production technique. However, there is only a little number of materials available for the process. In most cases parts are build up using polyamide 11 or polyamide 12. Therefore, parts produced with laser sintering sometimes do not have the required part properties for intended applications. Especially temperature stability or chemical resistance are sometimes not sufficient for parts made by polyamide 12. Cross-linking is a well established process for the post-processing of plastic parts in a cheap and fast single step treatment. It offers the possibility to improve temperature stability, the mechanical properties and the chemical resistance of parts. Therefore, it offers also great potential to improve part properties of laser sintered parts. However, there is only very limited knowledge on use of cross-linking for those parts. Within the performed work cross-linking is used to post-process parts made by laser-sintering. Two different laser sintering materials are considered in the study. On the one hand a standard polyamide 12 from EOS (PA 2200) is used. This is modified with a cross-linking agent on two different ways in order to test that influence on the resulting part properties. On the other hand a new polyethylene material from ROWAK, which was developed in person, is used for the tests. This material does not require an additional cross-linking agent. The laser sintered parts are cross-linked using two different radiation levels. Afterwards material and part properties like temperature stability and mechanical properties are studied for the cross-linked parts. Additionally, these results are compared to those of parts which were not treated. Results show a significant influence of cross-linking on the performance of laser sintered parts with an improvement of some properties.