This paper reports on numerical simulations of the hydrodynamics inside droplets in rectangular microchannels. Two- and three-dimensional simulations are performed thanks to a finite-volume/front-capturing method. Droplet interface deformation and velocity fields inside both droplets and continuous phase can then be followed. This study leads to important results about droplet deformation and inner streamlines for mass and heat transfer studies. More particularly, the capillary number seems to have a great influence on the liquid/liquid flow hydrodynamics and this impact on film thickness and slip velocity is quantified through correlations.