Since the discovery that CO acts as a cytoprotective and homeostatic molecule, increasing research efforts have been devoted to the exploitation of its therapeutic effects. Both endogenous and exogenous CO improves experimental lung, vascular and cardiac injuries and protects against several inflammatory states. The technology is now in place to bring CO to clinical applications, but the use of the gaseous molecule poses several problems. The challenges associated with the clinical implementation of the gas have in part been answered by the development of CO-releasing molecules (CO-RMs). As stable solid forms of CO, these molecules represent an alternative to the administration of carbon monoxide (orally or by injection). In this article, we present insights into the biochemical action of CO and discuss the efficacy of CO and CO-RMs in preclinical disease models. Recent advances in the CO-RMs field are critically addressed.