We evaluated postoperative pain intensity using the PainVision system for quantitative pain analysis and assessed the correlation with numerical rating scale( NRS) for subjective pain evaluation. Twelve patients were evaluated for both pain intensity by PainVision and values by NRS at 6, 24 and 48 hours following after thoracic surgery. The correlation coefficient between pain intensity and NRS values was 0.20, which suggested that degrees of pain measured by subjective and quantitative pain scales were not necessarily consistent. Assessing pains with both conventional subjective pain evaluation and quantitative pain intensity evaluation by PainVision is possibly useful in providing optimal postoperative pain management.