Background: Diaphragmatic muscle dysfunction is common among mechanically ventilated COPD patients which leads to weaning failure. Bedsides Diaphragmatic US can be used to predict the extubation outcome. Aim: To study the value of chest Ultrasonography in the assessment of both diaphragmatic excursion and thickness as a weaning parameter in mechanically ventilated COPD patients. Patients and methods: The study was conducted on 48 mechanically ventilated COPD patients at the time of weaning in the respiratory ICU at Zagazig University Hospitals. The following were done: ABG, and chest X-ray. Ultrasonographic assessment of the right diaphragm (thickness and excursion) during SBT. The results: Patients were classified according to weaning outcome into two groups: the successful Weaning group (35 patients), and failed Weaning group (13 patients). Diaphragmatic excursion, tdi at end inspiration, tdi at end-expiration, tdi %, tdi % /f, and tdi % x Vt are significantly higher in the successful group (p<0.001). Diaphragmatic excursion and tdi at end inspiration are considered excellent significant discriminators for the success of weaning (P<0.000). tdi at end-expiration and tdi % is considered a good significant discriminator for the success of weaning (P<0.000). Integration of (Diaphragmatic excursion, tdi %, tdi % /f, tdi % x Vt, RSBI, PI max, PaO2/FiO2, and PEEP) can predict weaning success correctly by a percent of 65%. Conclusions: Diaphragmatic excursion is the most accurate, sensitive, and excellent discriminator for the prediction of successful weaning among diaphragmatic parameters. Integration of diaphragmatic ultrasound parameters and conventional weaning indices improves the successful weaning predictive value.