SummaryBehavioural changes in 85 two‐to‐ten‐year‐old children were evaluated by the parents one day, one week and one month after a routine ENT operation. Twenty (23%) children showed no changes. Behavioural problems at least once during the observation time were seen in 52 (61%) and improvements in 28 (33%) children, 15 (17%) had both. There was no statistically significant difference between the children treated as day cases and those hospitalized for one or two nights, or between the girls and the boys. The proportion of children showing behavioural problems decreased from 59% at 1 day to 32% at 1 month after the operation. The highest incidence of problematic changes occurred in children aged 3, 5 years or younger (79%), and the incidence was lowest in the 5.0–6.9‐year‐olds (43%). The most common changes were an increase in seeking attention from the parents (in 34% of the children), temper tantrums (25%), waking up at nights (16%) and problems in