We report the broadening and shifting of the Raman Q branch lines in D2and D2‐ He mixtures, all at 305.2 K. From a linear fit of the widths and shifts as a function of density we have determined broadening and shifting coefficients with an uncertainty of ±0.5%. None of the existing semi‐classical or quantal coefficient agree with the measurements at this level of accuracy. As well we discuss nonlinear contributions to the widths and shifts. Measurements of the broadening of the depolarized part of the Q branch in D2are reported for the first time.