Bladder infiltration by leukemia or lymphoma is rare and can mimic benign processes such as follicular cystitis (FC). Materials and methods: Eight benign and malignant hematologic diseases encountered in urine cytology were retrospectively reviewed for clinical, radiographic, and cytologic findings. Results: There were 2 cases of acute myeloid leukemia, 2 cases of diffuse large B-cell lymphoma, and 4 cases of FC. The most common presenting symptom was hematuria. Imaging findings included echogenic debris within the bladder or an adjacent soft tissue mass in acute myeloid leukemia cases and bladder wall thickening in diffuse large B-cell lymphoma cases. No FC cases had any imaging abnormalities. Cytologic material of the leukemia cases showed numerous myeloid blasts with markedly increased nuclear-to-cytoplasmic ratios, centrally located nuclei, inconspicuous nucleoli, nuclear indentations, and some irregular nuclear membranes. The background showed sparse urothelial cells and histiocytes. Both lymphoma cases showed a discohesive population of atypical large lymphoid cells with irregular nuclear borders and prominent nucleoli. The FC cases had a background lymphoid cell population with a maturation spectrum from small lymphocytes to large lymphoid cells (immunoblasts) and histiocytes including tingible body macrophages. Additionally, there were many mature squamous cells and reactive urothelial cells. Conclusions: Bladder leukemia, lymphoma, and FC are infrequently encountered on urine cytology. FC can be distinguished from a hematologic malignancy by the presence of a lymphocytic maturation spectrum and tingible body macrophages. Radiologic abnormalities are associated with malignant processes; however, discrete bladder masses are usually not identified.