Background: Long COVID significantly impacts various body systems, particularly the respiratory system. This study aimed to analyze the lung ventilatory function and diffusion capacity of patients with severe SARS-CoV-2 pneumonia at different time points during a 24-month follow-up course. Methods: Ventilatory function and lung diffusion capacity of the lung were assessed 6, 12, 18, and 24 months after hospital discharge. Patients underwent spirometry and lung volume measurements. Ventilatory parameters and DLCO and KCO normalization were defined as achieving values > 80% predicted. Results: A total of 222 patients admitted to the Intensive Care Unit (ICU) of the ASST - Spedali Civili di Brescia, Brescia, Italy, who survived severe SARS-CoV-2 pneumonia were enrolled. Among the 172 patients who completed the study, 140 (85.59%) achieved normalization of ventilatory parameters and DLCO and KCO. The median time to recovery was 4.5 months, and the hazard ratio (HR) reduced by 2% as each year of age increased. The median time to normalize ventilatory parameters (VC, FVC, FEV ₁, Tiffeneau index, TLC, and KCO) was 1.5 months, while the median time to VA normalization was 4.5 months. Male gender reduces the normalization odds of the Tiffeneau index and Alveolar Volume (VA). The median time to DLCO normalization was 9 months, with HR reduced by 3.1% as each year of age increased and augmented by 226% in obese subjects. Conclusions: 24 months after hospital discharge, 19% of patients had persistent ventilatory and/or diffusive defects. Our study documented that male sex, age, and obesity impact the normalization odds of ventilatory function and diffusive capacity of the lung. These findings underline the chronic nature of lung damage following severe COVID-19 pneumonia and the need for long-term follow-ups .