Cardiac catheterizations are among the X-ray procedures with the highest patient radiation dose and therefore are of great concern in pediatric settings. This study aimed to evaluate factors that influence variability of X-ray exposure in children with congenital heart diseases during cardiac catheterization. The study included 107 children who underwent either diagnostic (n = 46) or interventional (n = 61) procedures. A custom-made sheet for patient and procedural characteristics was designed. Data were collected, and different correlations were applied to determine factors that influence variability of X-ray exposure. The flouroscopy time (FT) differed significantly between the diagnostic (8.9 ± 6.3 min) and intervention (12.8 ± 9.98 min) groups (P = 0.032). The mean dose–area product (DAP) differed significantly between the two groups (3.775 ± 2.5 Gy/cm² vs. 13.239 ± 15.4 Gy/cm²; P = 0.003). The highest DAP was during left anterior oblique (LAO) cranial 30° angulation (2.8 Gy/cm²/4 s cine). The mean cumulative dose (CD) was 0.053 Gy in diagnostic cases and 0.48 Gy in intervention cases. The effective dose was 5.97 ± 7.05 mSv for theraputic procedures compared with 3.42 ± 3.64 mSv for diagnostic procedures. The FT correlated significantly with both the DAP (r = 0.718; P < 0.001) and the CD (r = 0.701; P < 0.001). Other correlations were reported. An increasing number of therapeutic catheterization procedures are being performed for children. The justification for these procedures is evident because they avoid complicated surgery. However, the complexity of these procedures results in higher radiation exposures.