Compression of ultrashort fundamental solitons in dispersion decreasing fibers (DDFs) with negative third-order dispersion (TOD) is investigated by solving the generalized nonlinear Schrdinger equation numerically. We have shown that, in contrast to the degradation of soliton compression due to the combined effects of positive TOD and Raman self-scattering (RSS), the combined effects of negative TOD and RSS can significantly enhance soliton compression in DDF′s. The enhancement is due to RSS induced redshifting of the soliton wavelength and the negative TOD induced decrease of second-order dispersion toward the longer wavelength.