Once diagnosed as "cell paucity"or "atypia" by the cytospin (CS) preparation, this CS preparation does not secure a precise diagnosis by repeated testing alone. Although the ThinPrep (TP) preparation is acknowledged to show increased cellularity, performing the screening tests for the cases that have enough cellularity, according to CS, raises issues for the cost-effectiveness. To obtain a more precise diagnosis through increasing the cellularity by performing TP, we selected the cases that were diagnosed as "cell paucity" or "atypia" by CS, but they required a more precise diagnosis, and the samples were processed via both CS and TP to compare the results. 11 patients diagnosed as "cell paucity" and 22 patients diagnosed as "atypia" by CS participated in this study. When the detection rate of atypical cells in both preparations with repeated urine cytology was compared, the overall detection rate of TP (16cases, 48.5%) was superior than that of CS (11cases, 33.3%), with statistical significance. The cellularity of both preparations was compared on repeated urine cytology; the general cellularity of TP (29cases, 87.9%) was higher than that of CS (20cases, 60.6%), but there was no statistical significance. Particularly, we repeated the TP for the 1 case that was diagnosed as "atypia" and we performed polyoma virus immunohistochemical staining, which confirmed polyoma virus. In conclusion, we can avoid obtaining negative diagnosis from cases with uncertain "atypia" or "cell paucity" by performing repeated TP testing.