qgis - Select all polygons that are completely within a circular buffer

I made several buffers around some points. Now I want to select all polygons that are completely within this buffer. My problem is that I also get the polygons that are partially outside of the buffer.

Answer

You should use "Vector->Research tools->Select by Location" and check the "Use selected features only" box. You will want to include ONLY:

Include input features completely within the selection features

https://docs.qgis.org/2.6/en/docs/user_manual/processing_algs/qgis/vector_selection_tools/selectbylocation.html