Among the Polychaeta collected by the expeditionary research vessel “Vityaz” from the deepest areas of the Pacific trenches – the Marian, Tonga and Kermadec – there were found three new species: Macellicephala bicornis sp. n. Poecilochaetus vitjazi sp. n., Pseudoscalibregma pallens sp. n. described in the present paper. The comparative study of the polychaetous fauna of these trenches shows the significant difference of the polychaete population in each of the mentioned trenches.