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Background To assess subfoveal choroidal thickness (SFCT) and its associations in school children in a Russian population.Methods The Ural Children Eye Study (UCES), a school-based case-control study, was performed in Ufa/Bashkortostan/Russia from 2019 to 2022 and included 4933 children (mean age: 9.7±2.6 years; range: 6.2–18.8 years). The children underwent a series of ophthalmological and systemic examinations. Optical coherence tomographic (OCT) images of the macula were obtained in a randomly selected subgroup.Results Out of 4933 children primarily participating in the UCES, a randomly selected group of 1462 (29.6%) children underwent OCT. Thicker SFCT (mean: 322±82 µm; median: 317 µm; range: 105–691 µm) was associated (multivariable analysis) with the systemic parameters of older age (beta: 0.15; B: 3.99; 95% CI 0.91, 7.08; p=0.01), taller body height (beta: 0.17; B: 0.78; 95% CI 0.27, 1.29; p=0.003), earlier school start in the morning (beta: −0.07; B: −5.60; 95% CI −9.42, –1.88; p=0.004), lower prevalence of actively resting during studying (beta: −0.06; B: −8.80; 95% CI −15.6, –1.98; p=0.01) and earlier time of going to bed in the evening (beta: −0.07; B: −0.68; 95% CI −1.20, –0.15; p=0.01), and the ocular parameters of shorter axial length (beta: −0.59; B: −46.8; 95% CI –53.0, –40.5; p<0.001), lower corneal refractive power (beta: −0.18; B: −10.3; 95% CI −23.9, –6.81; p<0.001) and deeper anterior chamber depth (beta: 0.12; B: 36.4; 95% CI 17.7, 55.2; p<0.001). It was not significantly associated with sex (p=0.87), body Mass Index (p=0.88) and best-corrected visual acuity (p=0.18). Mean inter-eye SFCT difference (39.3±35.5 µm; median: 30 µm; range: 0.00–259 µm) was related with inter-eye difference in axial length (beta: −0.29; B: −57.1; 95% CI –66.9, –47.4; p<0.001).Conclusions In this ethnically mixed school children population from Russia, in contrast to studies on adult individuals, SFCT increased with older age. As in adults, however, at a more marked degree compared with adults, it decreased with longer axial length, by approximately 47 µm for each mm of longer axial length in multivariable analysis.