A.V. Sakellaropoulou, M.N. Hatzistilianou, M.N. Emporiadou, V.T. Aivazis, J. Goudakos, K. Markou, F. Athanasiadou-Piperopoulou achieve statistical significance if they are observed only in small samples, as in our groups. A confidence interval is a measure of how much trust can be placed in an estimate derived from a sample, taking into account the scope for chance variation from one sample to another. The larger the size of a sample, the narrower the confidence interval that will be obtained. This reflects the fact that bigger samples provide more information and therefore allow more confident conclusions with a smaller range of uncer- tainty. Thus, one of the disadvantages of our study was the small sample size limiting the possibility to obtain statistically significant differences, and which explains the wide range of 95% CI. But, our study is the second study performed in Greece that correlates the presence of NE in children diagnosed with PSG as having OSAHS [33]. Thus, future studies in larger populations would probably provide further informa- tion on whether and to what extent nocturnal enuresis is observed in OSAHS children. Finally, if our findings are verified with multi-centre studies of patients-controls, sleep apnoea should be included in the differential diagnosis of children with nocturnal enuresis. We should also mention that none of the children with NE received any medical treat- ment, although urinary tract abnormalities and infec- tion as well as psychological factors and constipation have previously been excluded. In conclusion, the co-existence of mouth breathing, snoring almost every night, nasal congestion or a high threshold of arousals during sleep should be more ca- refully evaluated in cases of children with nocturnal enuresis who do not respond to standard treatment. Thus, in these cases, paediatricians who treat chil- dren with enuresis should consider the possibility of OSAHS. 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