Objectives: Conducting a retrospective analysis of the clinical characteristics and evolution of patients with spinal muscular atrophy (SMA) type 1 and 2 which were treated with the new modifying therapies. Methods: A descriptive, cross-sectional and retrospective study was conducted with a target population of patients with a genetic diagnosis of SMA treated with nusinersen or onasemnogene abeparvovec-xioi (OAX) who were monitored by the external consultation services of pediatric pulmonology in a tertiary hospital. The data were collected from their electronic clinical records. Results: The study describes 6 patients with ages from 14 months to 11 years, 4 of whom had a diagnosis of SMA type 1 and 2 with a diagnosis of SMA type 2. With regard to their treatment, 3 patients received nusinersen, 2 patients received OAX, and 1 patient received OAX followed by nusinersen. The number of emergency consultations due to respiratory infections per year of treatment was 0.3/year for patients treated with OAX and 0.75/year for patients treated exclusively with nusinersen. None of the patients treated with OAX have required hospitalization for a respiratory infection to date. With regard to respiratory support, two patients had a tracheostomy, and the rest received nocturnal noninvasive mechanical ventilation as a preventive measure. Two of the patients had undergone gastrostomy. The patients treated with OAX have shown an improvement in their motor functions according to the CHOP INTEND score. Conclusions: The description of different real-life cohorts will make it possible to homogenize the management of these patients and provide realistic expectations regarding the evolution of their condition.