The sedimentation rates and diffusive sediment mixing coefficients at several Lake Ontario locations have been derived from measurements of unsupported210Pb profiles in sediment cores. The values of mixing coefficients obtained in the present study are significantly lower than those obtained previously through an analysis of porosity profiles. The present estimates, however, are consistent with the rather well-preserved pollutant profiles at some of these locations. It is observed that the more realistic value of the mixing coefficient, obtained by inclusion of the sedimentation rate parameter, follows the sign opposite to that for the constant obtained by regression analysis of the porosity data. Further work is required to delineate this apparent relationship between two important physical characteristics of deposited sediments.