Optimization is one of the radiation protection efforts by giving radiation doses to patients as low as possible without reducing the quality of clinical images or what is often referred to as ALARA (As Low as Reasonably Achievable). A Diagnostic Reference Level (DRL) is an investigative indicator to optimize radiation protection for diagnostic and interventional radiology patients. The typical radiation dose value in AP thoracic examination patients at Gading Pluit Hospital is higher than the Indonesian DRL (I-DRL) value, so it is necessary to optimize the dose. Optimization of radiation dose aims to protect patients by evaluating exposure factors without compromising the quality of clinical images. AP chest image acquisition was performed using clinical exposure factors and their variations on the general radiographic X-Ray Listem REX 525-R. Evaluation of dose and image quality was carried out by a reading doctor/radiologist using a blind test. Optimizing results show that a lower exposure factor can reduce the radiation dose in AP thoracic examination of adult patients without affecting image quality. Exposure factor 80 kVp; 150 mA; 3.75 mAs is recommended to replace the exposure factor used before optimization, namely 80 kVp; 200 mA; 7 mAs. Keywords: optimization, DRL, radiation protection.