Cystic fibrosis (CF, OMIM: #219700), caused by biallelic pathogenic variations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene, is the most common monogenic disease. The present study aimed to investigate CFTR gene variations in patients with a positive screening test result for CF and those with a clinical suspicion of CF. Overall, 443 patients (190 females/253 males) were retrospectively included. Of these, a positive neonatal screening test result for CF was reported in 124 patients (58 females/66 males) and a preliminary clinical diagnosis of CF based on recurrent lung infection and/or delayed weight gain was reported in 327 patients (134 females/193 males). All patients were evaluated based on clinical findings, sweat test (ST) results, and CFTR gene sequence analysis results. In the group of 116 patients having a positive neonatal screening test result for CF, heterozygous variations were observed in 21 (18%) patients, compound heterozygous variations in 9 (8%) patients, and homozygous variations in 5 (4%) patients. In the group of 327 patients with a clinical suspicion of CF, heterozygous variations were observed in 52 (16%) patients, compound heterozygous variations in 26 (8%) patients, and homozygous variations in 11 (3%) patients. When the two groups were cumulatively evaluated, the most common mutant alleles were Pro1013Leu (10.4%), Tyr515* (9.6%), and Phe508del (4.8%). In the total study sample of 443 patients, 51 different variants were detected. To the best of our knowledge, this is the first comprehensive study that demonstrated CFTR gene variation distribution in the Eastern Anatolia Region of Turkey. In this study, mutation distribution was highly heterogeneous, and we believe that investigation of the entire CFTR gene is necessary and would improve the diagnostic rates for CF in the Turkish population.