A lung computed tomography (CT) scan is essential for diagnosing lung diseases in hematopoietic stem cell transplantation (HSCT) recipients. As a result, lung CT scans are increasingly prescribed in the early phase after allogeneic HSCT, with no assessment of the added value for global patient management. Among 250 patients who underwent allogeneic HSCT in our center over a 2-year period, we evaluated 68 patients who had at least 1 lung CT scan within the first 30 days post-transplantation. The median interval between allogeneic HSCT and lung CT scan was 8.5 days. Patients who underwent an early lung CT scan were more immunocompromised and had a more severe course. Fever was the main indication for the CT scan (78%). The lung CT scan was abnormal in 52 patients, including 17 patients who had an abnormal pre-HSCT CT scan. A therapeutic change was noted in 37 patients (54%) within 24 hours after the lung CT scan. The main changes included the introduction of corticosteroids (n = 23; 62%), especially in patients with a normal CT scan (89%). In univariate models, we found that a normal pretransplantation CT scan (P = .002), the absence of either dyspnea (P = .029) or hypoxemia (P = .015), and a serum C-reactive protein level <10 mg/L (P = .004) were associated with a normal post-HSCT lung CT scan. We found that the association of these variables could predict the normality of early post-HSCT lung CT scans. Pretransplantation lung CT scans are useful for the interpretation of subsequent lung CT scans following allogeneic HSCT, which are frequently abnormal. Early post-HSCT lung CT scans are helpful in patient management, but prescriptions could be more targeted.