PurposeOur aim was to explore the applicability of the definition of “large” primary spontaneous pneumothorax (PSP) of adult guidelines to pediatric patients.MethodsWe performed a retrospective monocentric analysis of first‐episodes of PSP (Period: January 2010–January 2023). We defined large PSP according to French SPLF/SMFU/SRLF/SFAR/SFCTCV Guidelines. Inclusion criteria: age 1−18 years‐old, follow‐up ≥ 1 year. We performed a comparative analysis between large and nonlarge PSP. We reported the categorical variables as frequencies, and continuous as median and range. We compared categorical variables using Chi‐Square or Fisher test, and continuous using U Mann–Whitney test. p < 0.05 was considered significant.ResultsThe population consisted of 49 patients, 15 (30%) with large PSP. We found no significant differences at presentation between large and nonlarge PSP regarding age, sex, side, BMI, oxygen saturation, respiratory rate and hearth rate. Conservative first‐line management was used significantly less for large PSP (26% vs. 82%, p = 0.0003), while drain more (46% vs. 8%, p = 0.005). The groups were similar regarding surgery. Large PSP had a significantly longer hospitalization (7 days vs. 4 days, p = 0.003). The incidence of first‐line management failure was similar between the groups. During the follow‐up, we found no significant differences regarding ipsilateral recurrence (33% vs. 17%, p = 0.275), and contralateral occurrence (0% vs. 5%, p = 1.000), need for drain (6% vs. 5%, p = 1.000), or surgery (33% vs. 14%, p = 0.246).ConclusionsIn the first‐line, large PSP were treated significantly less conservatively and more drained. Radiographic size of the pneumothorax does not seem to have an impact on first‐line treatment failure and follow‐up outcomes.