State-of-the-art CT scanners typically display two dose indices: CT dose index (CTDI(vol) [mGy]) and dose length product (DLP [mGy-cm]) based on one of two standard CTDI phantoms (16- or 32-cm diameter) used in the calculation of CTDI(vol). CTDI(vol) represents the radiation produced by the CT scanner, not the radiation dose to an individual patient. Pediatric radiologists, aware of this discrepancy, have requested a method to estimate the CT patient dose based on the size of the pediatric patient or small adult. This paper describes the method developed by AAPM Task Group 204 to provide a better estimate of CT patient dose. These improved estimates of patient dose provide radiologists with a practical tool to better manage the radiation dose their patients receive. In the future, size-specific dose estimates (SSDE) received by the patient should be included in the patient's electronic medical record to help radiologists better assess risk versus benefit for their patients.