The series of the dyes possessing diazine residue have been investigated as visible-light absorbing photoinitiators of free radical polymerization. The rates of photoinitiation depend on the structure of the dye. Mechanism of the photoinitiation involves the electron transfer process between the dye and the electron donor (co-initiator). The dyes possessing diazine residue in the presence of a suitable electron donor are very effective photoinitiators. This can be attributed to the high quantum yield of their triplet state formation and high rate constant of electron transfer reaction between the dye and electron donor.