© 2017 American Roentgen Ray Society. OBJECTIVE. The purpose of this study was to evaluate the impact of trainee involvement and other factors on addendum rates in radiology reports. MATERIALS AND METHODS. This retrospective study was performed in a tertiary care pediatric hospital. From the institutional radiology data repository, we extracted all radiology reports from January 1 to June 30, 2016, as well as trainee (resident or fellow) involvement, imaging modality, patient setting (emergency, inpatient, or outpatient), order status (routine vs immediate), time of interpretation (regular work hours vs off-hours), radiologist's years of experience, and sex. We grouped imaging modalities as advanced (CT, MRI, and PET) or nonadvanced (any modality that was not CT, MRI, or PET) and radiologist experience level as = 20 years or > 20 years. Our outcome measure was the rate of addenda in radiology reports. Statistical analysis was performed using multivariate logistic regression. RESULTS. From 129,033 reports fnalized during the study period, 418 (0.3%) had addenda. Reports generated without trainees were 12 times more likely than reports with trainee involvement to have addenda (odds ratio [OR] = 12.2, p < 0.001). Advanced imaging studies were more likely than nonadvanced studies to be associated with addendum use (OR = 4.7, p < 0.001). Reports generated for patients in emergency or outpatient settings had a slightly higher likelihood of addendum use than those in an inpatient setting (OR = 1.5, p = 0.04; and OR = 1.3, p = 0.04, respectively). Routine orders had a slightly higher likelihood of addendum use compared with immediate orders (OR = 1.3, p = 0.01). We found no difference in addendum use by radiologist's sex, radiologist's years of experience, emergency versus outpatient setting, or time of interpretation. CONCLUSION. Trainees may add value to patient care by decreasing addendum rates in radiology reports.