Measurements of the third-order susceptibilities of new dithienylethylenes in solutions using a degenerate four wave mixing technique at λ=532 nm in picosecond regime were made. From these measurements we deduced the second order hyperpolarizabilities. Optical power limiting properties of the mentioned compounds using nanosecond laser pulses in the visible range are evaluated. The dispersion of nonlinear absorption coefficients is obtained. The appropriate quantum chemical calculations are carried out.