Background: . Mechanical ventilation (MV) is one of the most common interventions in critical care. Weaning from MV is one of the most frequently encountered challenges in modern intensive care units (ICU).  Weaning failure from MV occurred in 10-20% of  patients .our study is to predict liberation success from mechanical ventilation using noninvasive method as lung and diaphragm ultrasound. The aim is to evaluate and assess the value of lung and diaphragm ultrasound for predicting liberation success, using diaphragmatic thickening index “TI", modified lung ultrasound score (LUSm) and diaphragmatic rapid shallow breathing index (DRSBI). Methods: This a prospective observational study. The study involved 60 patients who were mechanically ventilated and planned for weaning trial on SBT using PSV mode. Ultra-sonographic assessment of lung and diaphragm was performed 30 min after SBT using the following indices; TI, DRSBI, and  LUSm a . Results: The patients with (TI) below 24, DRSBI more than 1.3 breath/min/mm and LUSm higher than 6 were experienced high risk of failed weaning. Conclusion:  DRSBI,TI and LUSm are sensitive non- invasive bed side sonographic indices that can predict liberation success  in mechanically ventilated patients. DRSBI is the best diagnostic predictor than TI and LUSmm, sensitivity 100% and 98.33% accuracy.