In 210 consecutive patients undergoing emergency central venous catheterization, we studied whether an ultrasonography examination performed at the bedside by an emergency physician can be an alternative method to chest X-ray study to verify the correct central venous catheter placement, and to identify mechanical complications. A prospective, blinded, observational study was performed, from January 2009 to December 2011, in the emergency department of a university-affiliated teaching hospital. Ultrasonography interpretation was completed during image acquisition; ultrasound scan was performed in 5 ± 3 min, whereas the time interval between chest radiograph request and its final interpretation was 65 ± 74 min p < 0.0001. We found a high concordance between the two diagnostic modalities in the identification of catheter position (Kappa = 82 %, p < 0.0001), and their ability to identify a possible wrong position showed a high correlation (Pearson's r = 0.76 %, p < 0.0001) with a sensitivity of 94 %, a specificity of 89 % for ultrasonography. Regarding the mechanical complications, three iatrogenic pneumothoraces occurred, all were correctly identified by ultrasonography and confirmed by chest radiography (sensitivity 100 %). Our study showed a high correlation between these two modalities to identify possible malpositioning of a catheter resulting from cannulation of central veins, and its complications. The less time required to perform ultrasonography allows earlier use of the catheter for the administration of acute therapies that can be life-saving for the critically ill patients.