Radiopharmaceuticals are used in nuclear medicine to obtain diagnostic findings based on justified clinical indications according to patient age, weight, and body mass index (BMI) to approve a reasonable low amount of attainable radiation dose without affecting the quality of the image. This study intended to assess patient effective dose in the cardiac, bone, thyroid and renal scan procedures. The current study was conducted at two nuclear medicine departments in Sudan (Al-Neeleen Diagnostic Centre (NDC) and Radiation Isotope Centre Khartoum (RICK)). A total of 193 procedures were performed at the two nuclear medicine departments using technetium 99m Tc isotope. Effective doses were estimated using computer software based on administered activity. The mean patients weight in cardiac, bone, thyroid and renal scans were 73.8±13, 64.8±19.6, 63.8±15.1, and 67.3±28.1 kg, respectively. The mean administered activity and effective dose per procedure were 810±246 and 7.1±2 for cardiac scan, 796.8±58.2 and 4.6±0.31 for bone scan, 195.1±21.2 and 2.6±0.27 for thyroid scan, and 198.6±32.9 MBq and 0.97±0.16 mSv for renal scan, respectively. Because administered activity depends on the procedure type and patient weight, it was 3 times higher in cardiac scan compared to thyroid scan. The results of this study revealed that patient's doses were lower compared to previous published studies.