The efficiency of different surface pretreatments (four standard chemical etchings and four diamond powder abrasive procedures) on silicon nitride (Si 3 N 4 ) substrates for chemical vapor deposition (CVD) of diamond has been systematically investigated. Blank Si 3 N 4 samples were polished with colloidal silica (ϳ0.25 m). 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 ϳ 10 10 cm ؊2 after 10 min), film uniformity, and grain size (below 2 m after 6 h) were obtained for the mechanically microflawed samples, revealing that chemical etchings (hot and cold strong acids, molten base or CF 4 plasma) are not crucial for good CVD diamond quality on Si 3 N 4 .