Urinalysis is important in the diagnostics but is often underestimated in veterinary practice. Its importance is most pronounced in the diseases of the urinary and endocrine systems, but recent research indicates its potential importance in diseases of other organ systems. This study aimed to determine the diagnostic significance of laboratory urine test results in making a final diagnosis in a gender and breed heterogeneous population of dogs with various diseases. The research processed the archival data of the laboratory of Clinic for Internal Medicine at the Faculty of Veterinary Medicine, University of Zagreb. The study included 141 results of dog urinalysis. Patients were grouped by gender (males and females), by weight into small (<10 kg), medium (10-25 kg), and large breeds (> 25 kg) and based on the final diagnosis into groups by organ systems. The significance of the urinalysis was determined based on the fact whether the results helped us to make a final diagnosis and was statistically validated. Diagnostic significance was found in 57,5% of the total population regardless of gender (p> 0.5). The significance of urinalysis is inversely proportional to the bodyweight of dogs and is 10% higher in small breeds compared to large ones, but no significant difference was found (p> 0.5). The results of urinalysis are of the greatest diagnostic importance in diseases of the urinary and endocrine systems (> 90%), while in patients with digestive and dermatologic disorders, which are the next most frequent urinalyses in dog patients, the contribution was significantly less in comparison to urinary and endocrine patients (p≤0.05). Its importance has also been noted in 64% of dogs with systemic disorders. The diagnostic significance of urinalysis concerning the organ system was most pronounced in the urinary and endocrine systems and systemic disorders, so we believe that collecting a urine sample by spontaneous urination in these patients is justified, while urinalysis in patients with digestive and dermatologic disorders is less important. It should be noted that this is, to our knowledge, the first study of diagnostic significance of urinalysis in a population with heterogeneous diagnoses to show insight into the actual state and importance of urinalysis in the dog population in Croatia