© 2020 EDIZIONI MINERVA MEDICA.BACKGROUND: This study aimed to evaluate the possible effect of anterior calyceal stones on the surgical outcomes of percutaneous nephrolithotomy. METHODS: Consecutive patients with complex kidney stones from 2012 to 2020 were evaluated retrospectively. In total, 219 patients were divided into 2 groups based on the presence of anterior calyceal stones (group 1; N.=89) or not (group 2; N.=130). The groups were compared in terms of surgical outcomes (i.e., stone-free rate [SFR], operation time, and hemoglobin drop) and complications. RESULTS: The patient demographics and stone characteristics were similar between the groups. Multiple access was more frequently done in group 1 than it was in group 2 (47.2% vs. 30.8%; P=0.014), and the SFR was lower in group 1 (51.7%) than it was in group 2 (67.7%; P=0.017). Of the anterior calyceal stones in group 1, 42.6% could not be cleaned. However, when excluding patients who have only anterior residual stones from the statistical analysis, the groups had similar SFRs (68.5% vs. 67.7% for group 1 and group 2, respectively). CONCLUSIONS: The presence of complex kidney stones with anterior calyceal extension are associated with higher residual stones rates in the anterior calyx. Also, it increases multiple access, the operation time, and level of hemoglobin drop.