Familial Mediterranean fever (FMF) is A common periodic fever syndrome. The causative gene of the FMF is named Mediterranean Fever gene (MEFV). Increased inflammation in FMF may play a role as a trigger for the development of some diseases. The objective of the study is to evaluate the frequency of comorbid disorders in children followed up with diagnosis of FMF. Additionally, we aimed to assess the association between FMF and other inflammatory conditions in a large pediatric FMF cohort. A total of 686 FMF patients were included in the cross-sectional study. A questionnaire including questions about characteristics of fever episodes, presence of arthralgia, arthritis, abdominal pain, chest pain during and co-existence of any other disease diagnosed by a physician was filled out by face-to-face interviews with patients or their parents. Female-male ratio was 0.85. Median age at the time of study, age at disease onset and at the time of diagnosis were 12.9 (1.7-22.3), 3 (0.08-17), and 6 (0.75-17) years, respectively. In 130 (18.9%) FMF patients we detected co-existing inflammatory condition. The most common co-existing diseases were: juvenile idiopathic arthritis 42 (6.1%), asthma/reactive airway disease 29 (4.2%), Henoch-Schonlein purpura 20 (2.9%), uveitis 12 (1.7%) and inflammatory bowel disease 10 (1.4%). Except for asthma/reactive airway disease and inflammatory bowel disease, there was no significant difference regarding the type of MEFV gene mutation. We have reported increased frequencies of various inflammatory conditions and decreased frequency of asthma in patients with FMF.