Background: Respiratory syncytial virus (RSV) is a common cause of hospitalisation in infants and children. This study aimed to identify common patient characteristics and baseline predictors of hospital length of stay (LOS) among infants diagnosed with RSV infection. Methods: This is a descriptive analysis of data from three separate prospective observational paediatric studies in Belgium, Japan, and New Zealand. Hospitalised children ≤5 years of age with a laboratory-confirmed diagnosis of RSV infection and an onset of symptoms ≤5 days prior to hospitalisation were considered for inclusion. We collected demographic and clinical information and the hospital LOS for each patient. LOS was assessed by age, presence of comorbidity, presence of prematurity, duration of symptoms and by country. Results: Overall, 181 patients were included in the analysis. The majority of patients (84%; 152/181) were otherwise healthy; only 16% (29/181) had comorbidity. Median hospital LOS was longer in Belgium and Japan than in New Zealand (5, 7, and 3 days, respectively). Presence of comorbidity prolonged hospital stay, with the effect on hospital LOS varying by country. Age, duration of symptoms prior to hospitalisation, and premature birth were not predictive of hospital LOS. Conclusion: In this cohort of children ≤5 years old hospitalised for RSV infection, medical practice varied greatly between countries. Although overall, comorbidity was associated with longer LOS, while other predictive factors were of little value in estimating LOS.