The photooxidative stability of poly(methyl acrylate), poly(ethyl acrylate), poly(ethyl methacrylate) and poly(butyl methacrylate) has been investigated under conditions of artificial solar light irradiation. Molecular and chemical changes induced by the light treatment were followed by size exclusion chromatography and Fourier transform infrared spectroscopy. The acrylate units were found to be more reactive towards oxidation, in comparison with the methacrylate ones. With short alkyl side groups chain scissions prevailed over cross-linking reactions both in acrylate and methacrylate samples. The degradation of poly(butyl methacrylate) proceeds in a completely different way, with extensive cross-linking and simultaneous fragmentation reactions. In all the samples the structure formed as result of oxidation reactions were similar. It has also been found that the first effect of degradation to be detected is that connected with the changes of samples molecular weight distributions.