Objectives: To evaluate the effect of informed consent format on preoperative anxiety of patients. Material and Methods: We performed a prospective study (91 patients) undergoing lower third molar extraction. Patients were distributed into three groups. Informed consent for surgery was obtained through a written document, an oral interview or a video recording. Afterwards, patients were asked about their anxiety level and the effect the informed consent had had on it. Results: Whereas the information conveyed both in oral and written formats relieved the patient to some extent (in a scale of -3 to +3) 0.97±1.21 and 0.29±0.97, respectively), the video recording increased patient’s anxiety in a statistically significant way (in a scale of -3 to +3, -0.57±1.43). The difference obtained between the values obtained in oral and written information was not statistically significant. Discussion: The most adequate format, according to our study, would be the oral format. Key words:Anxiety, satisfaction, third molar surgery, Spielberger State-Trait Anxiety Inventory.