Mass-screening for lung cancer is rather a unique system in Japan. This study illustrates time from finding abnormality on mass-screening to final diagnosis of lung cancer. Among the 517 patients with lung cancer who were admitted to our hospital over a 10-year period up to December 2001, 83 (16.1%) were detected by mass-screening. We reviewed medical records of the 83 patients and determined the intervals from the mass-screening to the pathological diagnosis with clinical staging. Time from the mass-screening to the date of hospital visit was <2 months in 62 (74.7%) cases. Five (6.0%) patients visited hospital more than 6 months after the mass-screening. With respect to the interval, there was no statistical difference in gender (p=0.0680) and age (p=0.1532). Among 60 patients who were referred from outside, on average, patients visited our hospital 0.5 month after they first sought medical attention at nearby clinic, and at our hospital 0.5 month was required to make a pathological diagnosis of lung cancer with TNM staging. There was a statistical difference in survival between the patients who were diagnosed <4 months and the patients who were diagnosed >4 months from the screening (p=0.0487). The interval in most cases was acceptable. However, further improvements are still needed to minimize the delay and to maximize the benefits of early cancer detection.