Introduction: The prevalence of caries, and its preferential location, has changed in recent years. The percentage reduction in caries has been lower in pits and fissures than in other locations, making it necessary to use more sensitive diagnostic procedures than visual inspection for approximal lesions. Objectives: The objective of this study was to compare the amount of overlooked proximal caries by bitewing X-rays versus clinical in patients who were completing a public oral health program at the age of 14 years. Methods: 162 children aged 14 years were clinically examined by a dentist as part of the systematic six-monthly dental check-ups of the children. The survey was carried out on dried teeth using a light, plane mouth mirror and blunt probe. All molar and premolar surfaces were examined in order to determine the presence of caries or restorations. In addition, two bitewing radiographs of each patient were obtained using a Klauser plastic parallelizer. Results: Caries lesions were diagnosed better by the X-rays than clinically (Δ X-ray = 0.61), whereas clinical examination was better at diagnosing the presence of fillings (Δ X-ray = - 0.03). Clinical examination diagnosed all occlusal caries but underestimated the interproximal lesions by 86.84%. Conclusions: In the context of public oral health programs, the authors consider it necessary to obtain two bitewing X-rays of the children's teeth before discharging them, as otherwise they could be told that they are healthy whereas, in fact, they present interproximal caries that could be treated by remineralization or restorative methods. Palabras clave: bitewing radiography, approximal caries diagnosis, dental caries