Cyclohexanone-formaldehyde and acetophenone-formaldehyde resin were in situ modified with phenol, Bisphenols, and substituted acetophenones. Furthermore, acetophenone-formaldehyde, cyclehexanon-formaldehyde, and in situ-modified resins were modified with anhydrides such as acetic anhydride, maleic anhydride, dodecenylsuccinic anhydride, 3,4,3’,4’-biphenyltetracarboxylic dianhydride, and 4,4’-oxydiphtalic anhydride. Modification of these resins with hydroxyl amine, semicarbazide, and phenyl hydrazine were also studied. Melting points, solubilities in organic solvents, FTIR, and NMR spectrum of the modified resins were determined.