Abstract of the Disclosure: Insoluble, only slightly swellable polymers containing amino groups, which can be obtained from popcorn polymers containing units of the structure ##STR1## where R and R.sup.1 are H or C.sub.1 -C.sub.4 -alkyl, by eliminating the group R--CO-- from at least 2% of the incorporated units of the structure I, with the formation of units of the structure II ##STR2## a process for the preparation of the amino-containing popcorn polymers by polymerizing N-vinylcarboxamides and, if desired, other monoethylenically unsaturated monomers copolymerizable therewith with from 0.1 to 10% by weight, based on the monomers used in the polymerization, of a compound containing at least two ethylenically unsaturated non-conjugated double bonds as crosslinking agent, with exclusion of oxygen and polymerization initiators, to form popcorn polymers, and elimination of formyl groups from at least 2% of the copolymerized N-vinylcarboxamides, and the use of the resulting insoluble, only slightly swellable polymers containing amino groups as ion exchangers or adsorber resins for metal ions are described.