Despite more accurate methods of cardiac imaging, plain chest X- ray (CXR) still is the first imaging modality in people with suspected heart diseases. The most important application of CXR in cardiac patients is the estimation of cardiac size. However, there are factors which may influence the cardiac size estimation some of these are technique used in CXR, age, sex, and BMI. Some chest radiography are done anterior – posterior, rotated film and with inadequate inspiratory efforts, this mainly due patients condition who are very sick and immobile, these parameters affect cardiac size estimation on chest radiography. Objectives: To assess the accuracy of cardiac size estimation on chest radiography at KCMC Radiology department and to determine the sensitivity specificity, positive and negative predictive value, negative likely hood ratio, positive likely hood ratio and diagnostic odd ratio. Methodology: A retrospective cross section study will be carried out for a period of 6 months in Radiology department of Kilimanjaro Christian Medical Centre. Study population will comprise adult patients sent to radiology department with cardiovascular symptoms who have chest x ray and echocardiography. Data collection sheet will be used to collect data on chest radiography findings and echocardiography findings. Echocardiography will be used as the gold standard. The sensitivity, specificity, positive predictive value and negative predictive value positive and negative likely ratio, diagnostic odd ratio will be calculated.