Precise measurements of plate heights of fused-silica columns with either cross-linked or conventionally coated stationary liquids were used to determine solute diffusion coefficients in these media. Three different methods of calculating liquid diffusion coefficients from chromatographic data were evaluated. The most accurate results were obtained by combination of plate heights for two different carrier gases. Contrary to expectation, no significant differences were found between diffusion coefficients in conventional or in situ cross-linked stationary liquids. Solute diffusion coefficients are listed for n-alkanes in CP-Sil-5, OV-1, CP-Sil-5-CB and OV-1-CB.