We discuss the effect of an homogeneous flow in the aggregation process of colloidal magnetic particles at moderate concentration. Situations in which the presence of flow acts in favor of the chaining process: particles assemble into chains larger than the ones emerging in the absence of flow, under the only influence of an externally imposed field, have been analyzed. The results we obtain follow from the analysis of the pair correlation function which, owing to the potential character of the flow we consider, can be interpreted in terms of a Boltzmann-type stationary distribution function. To render the influence of the flow on the resulting structures explicit, we study the particular cases of axisymmetric and planar elongational flows.