This research aims to provide innovation with regard to the obligation of means and the obligation of results in doctor-patient contracts, focusing the study on two specific medical procedures, which by their nature and characteristics represent a point of rupture and distinction between the obligations that the medical professional must guarantee, namely: medical-aesthetic procedures when they are performed for cosmetic reasons or merely for beautifying purposes, and when they are performed for corrective purposes. Establishing the nature of the contract that arises prior to a medical treatment is essential for the determination of the liability regime of the medical professional towards his patient, clearly establishing the contractual guidelines and the obligations to which the medical professional is subject.