We aimed to delineate cardiopulmonary interactions in acute bronchiolitis and to evaluate the capacity of a combined cardiopulmonary ultrasonography to predict the need for respiratory support. This was a prospective observational single-center study that includes infants < 12 month of age admitted to a hospital due to acute bronchiolitis. All the included patients under-went clinical, laboratory and cardiopulmonary ultrasonographic evaluation at the same time point within 24 hours of hospital admission. The existence of significant correlation between car-diac and respiratory parameters was the primary outcome. The association of different cardio-pulmonary variables with the need of respiratory support higher than O2, the length of stay hos-pitalization, the PICU stay, and the duration of respiratory support were a secondary outcome. We enrolled 112 infants (median age 1 (0.5-3) months; 62% males) hospitalized with acute bron-chiolitis. Increased values of the pulmonary variables (BROSJOD score, pCO2 and LUS) showed moderate correlations with NT-proBNP and all echocardiographic parameters indicative of pulmonary hypertension and myocardial dysfunction. Up to 36 (32%) infants required respira-tory support during the hospitalization. This group presented with higher lung ultrasound score (p<0.001), and increased values of Tei index (p<0.001) and pulmonary artery pressures (p<0.001). All the analyzed respiratory and cardiac variables showed moderate to strong correlations with the LOS hospitalization and the time of respiratory support. Lung ultrasound and echocardiog-raphy showed a moderate to strong predictive accuracy for the need of respiratory support in the ROC analysis, with AUC varying from 0.74 to 0.87. Conclusion: Those cases of bronchiolitis with a worse pulmonary status presented with a more impaired cardiac status. Cardiopulmonary ul-trasonography could be a good strategy to easily identify high-risk population for a complicated acute bronchiolitis hospitalization.