Background: The National Lung Screening Trial (NLST) demonstrated a 20% relative reduction in lung cancer mortality for current and former heavy smokers screened with low-dose CT vs. radiography. The NCCN and ACS recently released lung screening guidelines which promote smoking cessation counseling, but there is no information about the prevalence or effectiveness of brief physician-delivered smoking cessation interventions, such as the 5As (Ask, Advise, Assess, Assist, and Arrange follow-up) among lung screening patients. Methods: Among 8,878 NLST participants from 23 ACRIN sites who were smoking at enrollment, we conducted a longitudinal examination of the 1) rates and patterns of each reported 5A receipt and 2) association between each A and quitting. Using a case-control logistic regression, which matched participants according to trial arm; sociodemographic; medical; and smoking characteristics, we compared self-reported point-prevalence abstinence following 5A receipt. Results: Participants were 54% male, 90.6% white, and mean age 60.8 years. Receipt of 5As was consistent for the first 3 study years; rates of Ask (75%) and Advise (74%), exceeded rates of Assess (64%), Assist (58%), and Arrange follow-up (13%). Receipt of Ask, Advise, and Assess did not significantly increase the odds of a participant quitting smoking. Assist (cessation counseling, medication) increased the odds of quitting smoking by 22% (p=0.0002), and Arrange follow-up increased the odds of quitting by 20% (p=0.002). Older age and lower nicotine dependence were significantly associated with quitting, after accounting for the effectiveness of Assist (OR=1.34, CI: 1.16-1.55; OR== 0.95, CI: .93-.97) and Arrange follow-up (OR=1.34, CI: 1.16, 1.54; OR=.95, CI: .93-.97). Conclusions: Among high risk patients undergoing lung screening, Advice to quit was not associated with improved odds of smokers’ quitting. Assist and Arrange follow-up were associated with improved odds of smokers’ quitting, but unfortunately, rates of receipt of these As were low. Physician-delivered smoking cessation assistance and follow-up has the potential to enhance the effectiveness and cost effectiveness of lung screening. Clinical trial information: CDR0000257938.