In this paper some basic assumptions underlying the chemical derivatization analysis of polymer surfaces treated in nitrogen-containing plasmas are critically examined. Imines, which are known to represent major constituents of such surfaces as well as of plasma polymers grown from amine precursors, show a very versatile chemical reactivity. For example, imines are generally able to exchange their carbonyl component with aromatic aldehydes. Therefore, surface reactivity of polymers treated in nitrogen-containing plasmas with 4-trifluoromethyl-benzaldehyde (TFBA) or other benzaldehydes appears to be attributable not only to (primary) amines. Similar conclusions must be drawn for several other derivatization reagents.