Systemic inflammation is characteristic for preeclampsia (PE). A hypothesis for immune dysregulation is that the function of regulatory T cells (CD4+FoxP3+, Tregs) inhibiting the activation of lymphocytes is impaired. We investigated the proportion of Tregs and their cellular network in preeclamptic women. Fifteen preeclamptic and 17 healthy pregnant women were enrolled in the 32nd gestational week (median age 29 (range 22–45) and 32 (range 26–38) years, respectively). PE was diagnosed according to international criteria at a median of 30 gestational weeks (range 21–31). Peripheral blood was taken and blood mononuclear cells were isolated. Flow cytometry was used to determine the proportion of regulatory (CD4+FoxP3+) T cells, lymphoid and myeloid dendritic cells, natural killer and natural killer T cells, naive and memory and activated CD4+ and CD8+cells. The proportion of Tregs and that of naive CD4+CD45RA+ cells was lower in preeclamptic than in control women (p = 0.025, p = 0.04, respectively). The proportion of other investigated cell types did not differ. Low Treg numbers may support the notion that PE shares similar features to autoimmune disorders. Low Treg numbers are not reflected in the proportion of activated lymphocytes, at least in this stage of pregnancy. This does not exclude, however, the functional alterations of these cell types.