A new type of comb-like polymer which can lead to cross-polymerization was synthesized by modification of polyallylamine with 10-undecenoic acid containing a terminal vinyl group. Monolayer behaviour and structure of Langmuir-Blodgett (LB) films were studied for poly(allylamine-co-10-undecenoates) with different corepeat unit ratios. With increasing the corepeat unit ratio, the stability of monolayers was improved. Monolayers of slightly modified polymers (25% and 50%) were deposited on solid plates as non-alternating Z-type multilayers at low temperatures and high dipping speeds. In contrast, monolayers of highly modified polymers (70% and 80%) were deposited as alternating Y-type multilayers at higher temperatures and lower dipping speeds. It has been found that the cross-polymerization of these comb-like polymers with a high content of vinyl groups occurs easily in the LB films as a result of UV irradiation. Thermal stability and solvent resistivity of the films were enhanced owing to the two-dimensional network structure formed by the cross-polymerization.