Data from the National Lung Screening Trial (NLST) were examined by exploring different size thresholds for classifying CT screening scans as positive.  In the NLST, nearly two-thirds of nodules were 7mm in diameter or less.  Using a threshold of 5mm, the percentage of missed/delayed diagnosis and the likelihood of avoiding false positive findings were 1% and 16%.  Using a threshold of 8mm increased those rates to 11% and 66%.  Increasing size thresholds reduced follow-up CTs and invasive procedures.  Interestingly, differences in thresholds did not affect survival or mortality.