The present invention relates to novel 4-oxo-4H-pyrido[1,2-a]pyrimidine -3-carbonamide derivatives of the general formula (I) and the acid addition salts thereof, pharmaceutical compositions containing them and a process for their preparation. In the general formula (I) ##STR1## wherein: R stands for a C.sub.1-12 alkyl group optionally substituted by a C.sub.1-4 alkoxycarbonyl group; a C.sub.3-9 cycloalkyl, adamantyl or optionally substituted phenyl group;R.sup.1 means hydrogen or a C.sub.1-4 alkyl group; orR and R.sup.1 together form a --(CH.sub.2).sub.n -- chain, wherein n is 4, 5 or 6;R.sup.2 stands for hydrogen, a C.sub.1-4 alkyl group or halogen;R.sup.3 repesents hydrogen or a C.sub.1-4 alkyl group; andm is 0 or 1.The compounds of the general formula (I) possess a gastroprotective effect and are useful for the prevention and therapy of ulcers of the stomach and the small intestine.