The purpose of this study was to develop effective local dose reference levels (DRL) for SPECT/CT and PET/CT imaging in order to monitor and audit locally scanning protocols for the most frequent SPECT/CT and PET/CT imaging examinations performed at Sultan Qaboos University Hospital (SQUH). Thousand one hundred and thirty-four adult patients, who have undergone SPECT/CT and PET/CT scanning over a period of 4 years (2018-2021), were included in this study. The scans consisted of 401 PET/CT scans (whole body, brain and cardiac) and 733 SPECT/CT scans (bone, myocardial perfusion imaging (MPI), thyroid uptake, thyroid post ablation, and parathyroid). Low-dose CT scans were used for attenuation correction and localization. The PET administered activity was based on the patient's body-mass-index (BMI). The CT dosimetry data (CT dose index (CTDIvol), dose length product (DLP)) and the administered activities were collected. The third quartile was calculated for CTDIvol, DLP and administrated activity for each SPECT/CT and PET/CT examination. The PET/CT and SPECT/CT total effective doses (ED) were also derived. The estimated LDRLs are given as follows (third quartile CTDIvol (mGy):third quartile DLP (mGy.cm):third quartile administrated activity (MBq)): whole body PET/CT: 2.37:219.5:298; brain PET/CT: 12.86:301.7:270; cardiac PET/CT: 1.79:42.5:383; bone SPECT/CT: 3.18:135.3:814; MPI SPECT/CT (stress-rest): 1.77:60:821-809; parathyroid SPECT/CT: 3.52:140: 815; thyroid uptake (with I-131) SPECT: 4.36:189.5:207; thyroid post ablation 4.7:3.1. The estimated total ED (mSv) was: 7.5:7.8, 7.9:7.9, 6.9 :7.2 , 5.2:5.2, 7.4:7.8-7.3:7.7, 7.6:7.9, 4555:4555, 1.5:1.9 for (males: Females) whole body PET/CT, Cardiac PET/CT, Brain PET/CT, bone SPECT/CT, MPI SPECT/CT (stress-rest), parathyroid SPECT/CT, thyroid-uptake (with I-131) SPECT/CT, and thyroid post ablation SPECT/CT, respectively. The derived local DRLs has facilitated careful monitoring of doses delivered to patients and could act as a trigger to investigate doses that systematically exceeds the local DRLs set. Regular auditing of doses is expected to impact positively the department quality management program.