BACKGROUND Chest Ultrasonography (chest US) has shown good sensibility in detecting pneumothorax, pleural effusions and peripheral consolidations and it can be performed bedside. OBJECTIVE The aim of the study was to analyze agreement between chest US and chest X-ray in patients who have undergone thoracic surgery and discuss cases of discordance. METHODS Patients undergoing thoracic surgery were retrospectively selected. Patients underwent routinely Chest X-ray (CXR) during the first 48 h after surgery. Chest US have been routinely performed in all selected patients in the same date of CXR. Chest US operators were blind to both reports and images of CXR. Ultrasonographic findings regarding pneumothorax (PNX), subcutaneous emphysema (SCE), lung consolidations (LC), pleural effusions (PE) and hemi-diaphragm position were collected and compared to corresponding CXR findings. Inter-rater agreement between two techniques was determined by Cohen's kappa-coefficient. RESULTS Twenty-four patients were selected. Inter-rater agreement showed a moderate magnitude for PNX (Cohen's Kappa 0.5), a slight/fair magnitude for SCE (Cohen's Kappa 0.21), a fair magnitude for PE (Cohen's Kappa 0.39), no agreement for LCs (Cohen's Kappa 0.06), high levels of agreement for position of hemi-diaphragm (Cohen's Kappa 0.7). CONCLUSIONS Analysis of agreement between chest X-ray and chest US showed that ultrasonography is able to detect important findings for surgeons. Limitations and advantages have been found for both chest X-ray and chest US. Knowing the limits of each one is important to really justify and optimize the use of ionizing radiations.