Muscle dysfunction, defined as the loss of either strength or endurance properties of muscles, is a prominent comorbidity in chronic obstructive pulmonary disease (COPD) that leads to impairment of the patients' exercise capacity and quality of life. Chronic obstructive pulmonary disease skeletal muscle dysfunction may affect both respiratory and limb muscles. However, the latter are usually more severely affected. Importantly, survival and COPD mortality are negatively influenced by dysfunction of the lower limb muscles and poor muscle mass as measured by mid-thigh cross-sectional area. In the current review, we discuss the effects of skeletal muscle dysfunction and wasting on the outcome of COPD. Additionally, whether muscle dysfunction takes place in respiratory disorders other than COPD, such as cystic fibrosis, idiopathic pulmonary fibrosis, scoliosis, and pulmonary arterial hypertension along with critical illness, is also reviewed herein. Identification of skeletal muscle dysfunction should be included in the routine assessment of patients with chronic respiratory disorders and in critical care settings and should be considered as a relevant target for treatment. Corresponding author: Esther Barreiro, ebarreiro@imim.es