The efficiency of different surface pretreatments (four standard chemical etchings and four diamond powder abrasive procedures) on silicon nitride (Si3N4) substrates for chemical vapor deposition (CVD) of diamond has been systematically investigated. Blank Si3N4 samples were polished with colloidal silica (similar to0.25 mum). Diamond nucleation and growth runs were conducted in a microwave plasma chemical vapor deposition apparatus for 10 min and 6 h, respectively. Superior results concerning nucleation density (N-d similar to 10(10) cm(-2) after 10 min), film uniformity, and grain size (below 2 mum after 6 h) were obtained for the mechanically microflawed samples, revealing that chemical etchings (hot and cold strong acids, molten base or CF4 plasma) are not crucial for good CVD diamond quality on Si3N4.