Physiotherapists usually use auscultation and chest radiography to assess the patient and monitor their intervention. But these outcome measures have a low accuracy. The use of lung ultrasound by the physiotherapist to evaluate respiratory conditions of the patient offers new perspectives such as define indications for chest physiotherapy, evaluate its efficacy and adjust treatment in real-time. The objective of this review is to present how ultrasounds can be used for lung and diaphragmatic assessment at the bedside and to propose possible applications in chest physiotherapy. Lung ultrasound enables diagnosis of pleural effusion, pneumonia, atelectasis, pulmonary contusion, pulmonary edema and pneumothorax with high sensitivity and specificity. Sonographic evaluation of the diaphragm enables to quantify its motion, thickness and contractility. Understanding the lung ultrasound fundamentals and basic signs allows an accurate assessment of pleura, lung parenchymal and diaphragm. Lung ultrasound assesses lung aeration disorders and can guide the physiotherapist’s choice of techniques and parameters in chest physiotherapy. It is also an excellent tool for pleural assessment and may be a way to clarify indication of chest physiotherapy in pleural effusion. Diaphragm sonography enables to highlight in real-time diaphragm response to all chest physiotherapy techniques that are intended for this purpose. The use of lung ultrasound by physiotherapist needs to acquire solid knowledge in anatomy, pulmonary physiopathology and lung ultrasound semiology. Rigorous training and experience are requirements for lung ultrasound use within chest physiotherapy decision tree. The link between lung ultrasound signs, lung physiopathology and mechanisms of chest physiotherapy techniques allow us to imagine lung ultrasound as a powerful tool for diagnosis and monitoring in respiratory therapy.