Gas-liquid and liquid-solid mass transfers were studied in capillaries under Taylor flow regime. The influence of the capillary diameter, unit cell length and gas hold-up on measured k(L)a and k(S)a coefficients was correlated by simple correlation, which showed that in both cases the mass transport is mostly determined by the liquid slug length and velocity. The results demonstrated that the contribution of the mass transferred in the thin liquid firm surrounding the gas bubble is not dominant. The conclusions agreed with the predictions made on the basis of a model developed by means of RTD measurements which were carried out in the same capillaries. The results obtained during catalytic hydrogenation of nitrite ions can also be explained in view of new findings.