BACKGROUND Children with obstructive sleep apnea syndrome (OSAS) have impaired cortical processing of respiratory afferent stimuli, manifested by blunted sleep respiratory-related evoked potentials (RREP). However, whether this impairment is limited to respiratory stimuli, or reversible after successful treatment, is unknown. We hypothesized that, during sleep, children with OSAS have (1) abnormal RREP, (2) normal cortical processing of nonrespiratory stimuli, and (3) persistence of abnormal RREP after treatment. OBJECTIVE To measure sleep RREP and auditory evoked potentials in normal control subjects and children with OSAS before and after treatment. METHODS Twenty-four children with OSAS and 24 control subjects were tested during N3 sleep. Thirteen children with OSAS repeated testing 4-6 months after adenotonsillectomy. RESULTS RREP were blunted in OSAS compared with control subjects (N350 at Cz -27 ± 15.5 vs. -47.4 ± 28.5 μV; P = 0.019), and did not improve after OSAS treatment (N350 at Cz pretreatment -25.1 ± 7.4 vs. -29.8 ± 8.1 post-treatment). Auditory evoked potentials were similar in OSAS and control subjects at baseline (N350 at Cz -58 ± 33.1 vs. -66 ± 31.1 μV), and did not change after treatment (N350 at Cz -67.5 ± 36.8 vs. -65.5 ± 20.3). CONCLUSIONS Children with OSAS have persistent primary or irreversible respiratory afferent cortical processing deficits during sleep that could put them at risk of OSAS recurrence. OSAS does not seem to affect the cortical processing of nonrespiratory (auditory) afferent stimuli during sleep.