Diagnosis of gastric tumors in dogs is difficult and is often obtained by biopsy following identification of a mass through ultrasound (US) or endoscopy. In human medicine, modalities such as CT and endoscopy are standard of care in the diagnosis and staging of gastric tumors. Although one veterinary study has described CT findings of gastric tumors in dogs using iatrogenic gas dilation, there are no veterinary studies that have directly compared the usefulness of US versus CT in the diagnosis and staging of these tumors. This retrospective, descriptive study evaluated US and CT images from 13 dogs. Gastric tumor diagnoses included leiomyoma (n = 4), adenocarcinoma (n = 3), leiomyosarcoma (n = 3), gastrointestinal stromal tumor (n = 2), and lymphoma (n = 1). Computed tomography was successful in identification of 92% of gastric tumors, while US identified only 69%. Computed tomography identified more locations of lymphadenopathy and correctly identified the location of gastric tumors more frequently than US when compared to the surgical, endoscopic, or necropsy reports. Most features seen on US and CT overlapped between the different tumor types. Lymphoma had a lower mean attenuation in CT than the other gastric tumors and was the only gastric tumor to not have complete loss of the gastric wall layering on US. As expected, adenocarcinoma appeared as gastric wall thickening with regional lymphadenopathy.Findings supported using CT as an ancillary diagnostic test for characterizing and staging gastric tumors in dogs and assisting in the selection of surgical candidates. K E Y W O R D Sadvanced cross sectional imaging, canine, neoplasia, stomach INTRODUCTIONGastric tumors are rare in dogs, accounting for less than 1% of all neoplasms diagnosed. 1 The most common gastric tumor in dogs is adenocarcinoma, but tumors such as lymphoma, leiomyosarcoma, leiomyoma, extramedullary plasmacytoma, fibrosarcoma, gastroin-ABBREVIATIONS: GIST, gastrointestinal stromal tumor; US, ultrasound Previous publication or presentation disclosure: Presented in poster format at the 2019 National Veterinary Scholars Symposium in Worcester, MA EQUATOR network disclosure: EQUATOR network checklist was not used. testinal stromal tumor (GIST), mast cell tumor, and polyps are also reported. 2-4 Diagnosis is difficult and often occurs late in the disease process, making prognosis poor due to the likelihood of metastases. At this point of time, no clear consensus in veterinary medicine has been provided in regard to the selection of CT over ultrasound (US) in the detection and staging of patients with gastric neoplasia, especially if surgery is being considered. Delineating what diagnostic test is of value and highlighting limitations of modalities may help the radiologist and clinician to make better recommendations for their patients.Abdominal US and endoscopy have been the imaging modalities of