Photodegradation of two PAHs (anthracene and chrysene), two NPAHs (9-nitroanthracene, and 6-nitrochrysene) and seven MePAHs (1-methylchrysene, 2-methylchrysene, 3-methylchrysene, 4-methylchrysene 5-methylchrysene, 6-methylchrysene, 1-methylantracene, -methylantracene, 9-methylantracene) was studied in isooctane solutions exposed to the UV radiation from light simulator. Samples were placed in closed glass vials. PAHs and NPAHs were divided into three groups according to their life times. Degradation of all PAHs and NPAHs was faster in dichloromethane compared with isooctane. Decomposition of NPAHs was easier than degradation of corresponding parent PAHs. The most frequent photoproducts were quinone, benzoic acid and derivatives with hydroxyl, carbonyl and carboxyl groups for both PAHs and NPAHs. Chlorinated compounds were identified in dichloromethane. Degradation intermediates underwent further oxidation, fragmentation, reduction or radical chlorine addition in dichloromethane. Final degradation products of all PAHs were n-alcanes. Based on GC-MS data the mechanism of photoproducts formation was proposed.