The mass transfer within the T-shaped and cross-shaped micromixers have been studied using the CFD and confocal laser scanning microscopy methods. The concentration profiles, based on flow regimes, were used to compare the T and cross geometries. The cross-shaped micromixer tends to intensify the mixing and this is occurring for lower flow rates in comparison to the T shape. The improvement made by the cross geometry is attributed to the stronger vortex stretching and high shear rate, which reduces the liquid transfer length. Numerically, the presence of a single outlet in the T-shaped micromixer induces a smaller degree of freedom for the fluid. A higher pressure drop is calculated in the T-shaped micromixer in than the cross-shaped micromixer.