<p>This study evaluated the utility of rapid liquid-based cytology with a shortened fixation time for intraoperative effusion cytology compared to conventional smears. Despite widespread use, intraoperative applications of liquid-based cytology are understudied; no quantitative paired comparison of rapid liquid-based cytology and conventional smears under identical constraints has been reported. We therefore tested whether rapid liquid-based cytology enriches diagnostically informative cells during time-limited reads, supporting more reliable reporting. We retrospectively analyzed 67 effusion (17 adenocarcinoma-positive and 50 adenocarcinoma-negative) samples collected between May, 2019 and February, 2024. Smear area, nucleated cell counts per field and slide, atypical cell counts, and atypical cell aggregates were quantified for paired preparations and compared using the Wilcoxon signed-rank test. Rapid liquid-based cytology yielded a markedly small smear area with significantly high nucleated cell counts per field, and conventional smears yielded high total nucleated cell counts per slide. Rapid liquid-based cytology also revealed significantly high numbers of atypical cells and aggregates. Subgroup analyses based on specimen characteristics (mesothelial-dominant, blood-dominant, and mixed) confirmed that rapid liquid-based cytology yielded high per-field nucleated cell counts in all groups. These results suggest that rapid liquid-based cytology concentrates diagnostic cells into a small standardized smear area, supporting timely reporting.</p>