Lung transplantation (LTx) is an accepted treatment option for patients with end-stage lung disease who do not respond to non-transplant treatments. Lung transplantation (LTx) is an accepted treatment option for patients with end-stage lung disease who do not respond to non-transplant treatments. It is important to optimize the nutritional status of patients during the waiting period before transplantation, to positively improve their vital functions such as exercise capacity, to get up as soon as possible after transplantation, to shorten the hospitalization process and to support survival. Pulmonary rehabilitation (PR) aims to prevent further progression of respiratory disease and improve the physical and mental health of patients, as well as helping patients to adopt healthy behavior habits. PR before transplantation helps individuals maintain or optimize their functional status before surgery. PR before transplantation helps individuals maintain or optimize their functional status before surgery. Beta-hydroxy-beta-methylbutyrate (HMB) is an active metabolite of the branched-chain essential amino acid leucine. Several studies have shown HMB supplements to be beneficial, either alone or in combination with other amino acids and exercise training, for maintaining and restoring lean body mass, muscle strength and function in older adults. HMB provides a decrease in muscle protein breakdown along with an increase in muscle protein synthesis. In addition, it stimulates muscle protein synthesis by activating the mechanical target of the mammals are the target of rapamycin (mTOR) system and growth hormone/insulin-like growth hormone. Given the very low amounts of HMB and the low conversion rate of leucine to HMB (5-10%), the optimal dose requirement of HMB cannot be met with a standard diet. Therefore, oral supplementation of HMB is seen as an alternative to alleviate adult metabolic diseases, muscle wasting and functional loss. In lung transplant candidates, it is important to optimize nutrition and health conditions during the listing period, to get up as soon as possible after transplantation, to shorten the hospitalization process and to support survival. The study aimed to investigate the positive/negative effects of pulmonary rehabilitation and HMB supplementation, which supports muscle mass and protein production, on patients compared to pulmonary rehabilitation alone in lung transplant candidates.