Objective: We aimed to obtain reference values of three major vessels [Pulmonary artery (PA), aorta, superior vena cava (SVC)] diameters in fetuses between 20-24 weeks of gestation in the Turkish population and to evaluate the fetal heart anatomy. Material and Methods: Pregnant women who were evaluated in the Radiology Department were scanned by sonography in order to obtain fetal cardiac nomograms of the great vessels. Cardiac axis, size and three great vessels in addition to the four chamber view of the heart were evaluated. The cases were followed up postnatally with echocardiography and clinical evaluation. We calculated both the sensitivity and specificity of sonographic screening at the 20-24th gestational weeks. Also, we found the frequency of congenital cardiac disease. Nomograms were obtained by calculating average vascular diameter for each gestational week. Results: A total of 371 fetuses were evaluated in the sudy. The mean gestational age was 29.2±5.2. The mean diameters of PA, aorta and SVC were found as 4.28±0.51 mm, 3.70±0.54 mm, 2.45±0.45 mm, res- pectively. The ratio of PA/aorta was 1.17±0.14. The mean diameters of PA, aorta and SVC increased gradually between 20 and 24 gestational weeks (p values 0.001, 0.007 and 0.001; repeated measures ANOVA). In five cases a cardiac anomaly was detected (tetralogy of Fallot, one atrium one ventricle anomaly, ASD, PA wider than normal, aorta wider than normal,) sonographically. Of these five, three cases were confirmed by postnatal fetal echocardiography performed by pediatric cardiologists. Conclusions: This study represents the reference values for diameters of three great vessels of fetuses between 20 and 24 weeks in the Turkish population. The data obtained from our study will be a reference for future studies from our country.