The influence of the Schmidt number on the wall-to-liquid mass transfer in a packed bed reactor has been studied. It is shown that use of the classical dimensionless group Sh . Sc-1/3 and the particle Reynolds number Re(L) as a means of taking the effects of Schmidt number into account was not appropriate. The dimensionless group Sh’ . phi . Sc-0.41 . square-root beta and Re(Lw), based on an appropriate characteristic length and wall porosity were found to represent the wall mass transfer correctly as well as the wall heat-transfer coefficients obtained with different organic liquids.