Difluoro(iminio)methanides generated by the action of difluorocarbene on Schiff bases react with derivatives of maleic and fumaric acids, following the 1,3-dipolar cycloaddition pattern to give 2,2-difluoropyrrolidines which were detected by gas chromatography-mass spectrometry. The final products are stereoisomeric substituted 2-pyrrolidinones formed by hydrolysis of difluoropyrrolidines and their dehydrofluorination products, 2-fluoro-4,5-dihydropyrroles. The observed stereoselectivity of the cycloaddition suggests Z configuration of intermediate ylide and both endo- and exo-approach to the dipolarophile in the transition state corresponding to cycloaddition.