Thoracoscopic T2-T3 sympathicolysis (TS) is a minimally invasive treatment for patients suffering from severe, refractory essential hyperhidrosis (EH). TS has previously been shown to be safe and efficacious in children. In order to examine the effects of TS on respiratory function, pulmonary function tests (PFT) were performed prior to and 6 weeks and 6 months after TS in 12 children with EH (3 boys; mean age 12.8 ยฑ 2.5 years). Small asymptomatic decreases in forced expiratory volume in one second (FEV 1 ; -2%), forced expiratory flow after expiration of 75% of vital capacity (FEF 75 ; -9.6%), total lung capacity (TLC; -1%), transfer factor for diffusion of carbon monoxide (T LCO ; -7.6%), and transfer coefficient for diffusion of carbon monoxide (K CO ; -1.5%) were observed 6 weeks after TS. These changes are comparable to those observed in adults but did not reach statistical significance in small children. In line with observations in adults, TLC (and T L,CO ) returned to baseline values 6 months after TS, whereas FEV 1 , FEF 75 , and K CO remained at their 6-week level. In conclusion, TS causes only small, statistically insignificant, and asymptomatic decreases in pulmonary function in children. TS can, therefore, be considered a safe treatment option in children suffering from severe, refractory EH.