BACKGROUND፡ The cardiothoracic ratio (CTR) is a radiographic parameter commonly used in assessing the size of the heart. This study evaluated the gender and age-based differences in the average cardiothoracic ratios, and transverse cardiac diameters (TCD) of adults in Ghana.METHOD: Plain chest radiography reports of 2004 patients (without known chest related diseases) generated by two radiologists with at least 15 years’ experience from July 2016 to June 2020 were retrospectively analyzed for this study. The CTR for each radiograph was calculated using the formula CTR=(TCD÷TTD)×100, where TCD and TTD represent transverse cardiac diameters and transverse thoracic diameters, respectively. Data were analyzed with the statistical package for social sciences version 23. The independent t-test and One-way Analysis of Variance tests were used in the analyses.RESULTS: A total of 2004 patients’ chest x-rays were used in the analyses. The ages of the patients ranged from 20-86 years old with a mean of 39.4±14.04 years. The mean CTR for males was 46.6 ± 3.7% while that of females was 47.7±3.7%. The difference in the overall CTR among the gender groupings was statistically significant (p = 0.001). There were statistically significant differences between the gender categories among patients in the following age groups: 30-39 (p=0.046), 40-49 (p=0.001), 50-59 (p=0.001) and 60-69 (p=0.001).CONCLUSION: The study reveals there are significant gender and age-related differences in cardiac size parameters obtained from routine, frontal chest radiographs. These differences, if considered, may result in early and appropriate treatment of cardiac pathology in some age groups.KEYWORDS: Cardiothoracic ratio, Transverse cardiac diameter, Chest radiograph