S-Carboxymethylcysteine (carbocysteine or SCMC; also available in the lysinate form, SCMC-Lys) is a mucoactive drug, has antioxidant and anti-inflammatory properties. Carbocysteine has been recently recognized as an effective and safe treatment for the long-term management of COPD, able to reduce the incidence of exacerbations and improve patient quality of life. Moreover, carbocysteine was effective in counteracting some symptoms associated with cancer cachexia. Preclinical and clinical studies have demonstrated that the antioxidant and anti-inflammatory properties of carbocysteine are more important than mucolysis itself for its therapeutic efficacy. Therefore, carbocysteine may be able to reverse the oxidative stress associated with several chronic inflammatory diseases, such as cardiovascular diseases and neurodegenerative disorders.