Background: Primary retroperitoneal tumors (PRT) are a group of extremely heterogeneous soft tissue tumors that grow in the retroperitoneal space and have no organic affiliation. Tumors usually become symptomatically late and cause secondary symptoms or become palpable once they have become significantly large. Preoperative diagnosis of PRT is essential for assessing subsequent treatment tactics, planning the approach and volume of surgery, by detecting the structural component, relationships with adjacent anatomical structures and the degree of invasion. Material and methods: Complex prospective and retrospective analysis of clinical, anamnestic and imaging data of 118 patients with primary and nonprimary retroperitoneal tumors, investigated and treated at the Institute of Oncology of the Republic of Moldova during 2015-2020. Results: To determine the primary PRT diagnosis for the clinician, it is primordial to rule out the organic or secondary nature of the tumor. Thus, the patients were examined by: abdominal USG – 118 patients (100%), abdominal and small pelvic contrast-enhanced CT – 118 patients (100%), MRI – 3 patients (2.5%), videoesogastroduodenoscopy – 32 patients (27.1%), videocolonoscopy – 31 patients (26.3%), irigography – 4 patients (3.4%), urography – 29 patients (24.6%). Conclusions: Contrast-enhanced CT provides more accurate data than USG. The image obtained at the USG examination is flat, therefore the dimensional measurements of the tumor are not always performed on the longest tumor axis, especially in the case of polylobulated or giant tumors, while the tomographic examination techniques allow the three-dimensional reconstruction of the tumor with more accurate assessment of the tumor size.