OBJECTIVE. We evaluated central venous catheter motion causing misinterpretation of catheter tip location in pediatric patients and in an experimental model. MATERIALS AND METHODS. After the recognition of clinically significant catheter motion in 12 randomly selected patients, we conducted a prospective 2-month study of chest radiographs in our pediatric care unit and neonatal emergency department. Serial radiographs were examined for change in catheter tip position ascribed to motion artifact. An in vitro model was developed to replicate clinical parameters. Experimentally, catheter movement and exposure time were analyzed and their impact on catheter localization was recorded. RESULTS. In the 12 randomly selected patients, radiographic assessment of central venous catheter tip localization on sequential radiographs caused minor to major misinterpretation of the position of the catheter tip and even total nonvisualization of the catheterr. Ten (3.5%) of 352 prospectively interpreted pediatrric emergency department radiographs showed similar findings. Catheter motion that caused blurring was preproduced in vitro using radiographic parameters typically used in a clinical setting. Conclusion. Catheter motion can cause problems in assessing catheter tip position on pediatric emergency department chest radiographs. We reproduced this phenomenon in an in vitro model. Catheter removal or change in position may be mimicked by this artifact, and patient management may be affected. In our study, catheter localization was affected by catheter motion and exposure time.