Alterations in intracellular signaling pathways affecting immune cell activation, proliferation and differentiation of keratinocytes in psoriasis could explain the complex pathogenesis of the disease. NF-κB is one of the intracellular signaling pathways, which is involved in regulation of numerous pro-inflammatory genes, and affects the synthesis of pro-inflammatory cytokines directly involved in the development of psoriasis. The study was aimed to assess the number of cells with NF-κB translocation in lymphocyte populations of children with psoriasis depending in the disease severity and therapy. A total of 130 children with psoriasis vulgaris were examined. The comparison group included 30 healthy children. The study was conducted using the imaging flow cytometry Amnis ImageStreamX system. It was found that there were significant differences in the number of cells with NF-κB translocation in the lymphocyte populations of both children with psoriasis and comparison group. Children with psoriasis had a higher number of cells with NF-κB translocation in the populations of T helper cells, T_act, T_reg, and Th17 compared to healthy children (p < 0.05). The number of cells with NF-κB translocation in children with psoriasis correlated with the disease severity PASI (R_mul = 0.32) and BSA (R_mul = 0.31) scores, as well as with the disease duration (p < 0.05). NF-κB determination could be considered an additional criterion for the disease severity assessment in children with psoriasis. The differences in the degree of reduction of the number of cells with NF-κB translocation 24 h after administration of biologics (adalimumab, etanercept, ustekinumab) have been shown. Studying NF-κB in cell populations offers the prospect of understanding pathogenetic mechanisms of inflammation and developing new therapeutic methods for psoriasis.