Aim: By observing the expression and distribution of platelet-derived growth factor receptor alpha-positive (PDGFR alpha(+) cells in ureteropelvic junction obstruction (UPJO), to explore their role in the pathogenesis of children with congenital hydronephrosis. Materials and methods: The control group involved specimens of the normal ureter (nephrectomy for tumor; n = 10), and the UPJO group contained specimens of ureteropelvic junction (UPJ) segment excised during pyeloplasty (n = 30). The specimens were investigated using inununofluorescence for the expression and distribution of PDGFR alpha(+) cells in each group by light microscopy with computerized image analysis. Real-time PCR (RT-PCR) was used to study PDGFR alpha gene expression levels. In addition, small conductance calcium-activated potassium channel 3 (SK3) and closely associated cells consisting of smooth muscle cells (SMCs), interstitial cells of Cajal (ICCs), and nerve fibers were investigated. Results: PDGFR(alpha+) cells were in close proximity to SMCs, ICCs, and nerve fibers. PDGFR alpha(+) cells expressed SK3 channels, which are found to regulate purinergic inhibitory neurotransmission in SMCs. Regarding the expression of PDGFR alpha(+) cells no significant difference was seen between the two groups, while the expression of SK3 channels in PDGFR alpha(+) cells was significantly decreased in the UPJO group versus the control group. Conclusion: This study identified the expression of PDGFR alpha(+) cells in the human UPJ. Our results demonstrate the expression of SK3 channels in PDGFR alpha(+) cells was decreased in UPJO, and SK3 channels may be involved in the pathogenesis of UPJO by perturbing the UPJ peristalsis.