Aims: This study was planned to investigate the diagnostic utility of osmophobia as criterion for migraine without aura (MO) as proposed in the Appendix (A1.1) of the International Classification of Headache Disorders (ICHD-II, 2004). Methods: We analysed 1020 patients presenting at 10 Italian juvenile headache centres, 622 affected by migraine (M) and 328 by tension-type headache (TTH); 70 were affected by headache not elsewhere classified (NEC) in ICHD-II. By using a semi-structured questionnaire, the prevalence of osmophobia was 26.9%, significantly higher in M than TTH patients (34.6% vs 14.3%). Results: Osmophobia was correlated with: (i) family history of M and osmophobia; and (ii) other accompanying symptoms of M. By applying these ‘new’ criteria, we found an agreement with the current criteria for the diagnosis of migraine without aura (MO) in 96.2% of cases; 54.3% of previously unclassifiable patients received a ‘new’ diagnosis. Conclusions: In conclusion, this study demonstrates that this new approach, proposed in the Appendix (A1.1), appears easy to apply and should improve the diagnostic standard of ICHD-II in young patients too.