Objective To examine the feasibility of olfactory detection of lung cancer by trained sniffer dogs. Methods Three police dogs, one Labrador Retriever and two Springer Spaniels, went through the same training course on detecting odor markers of cancer and were subsequently used to differentiate 52 lung cancer patients and 30 healthy subjects. The sensitivity(true-positive rate)and specificity(true-negative rate)of the olfactory detection were calculated. The consistency of the sniffing outcomes was also compared. Results The Labrador Retriever had a sensitivity of 88. 46% and a false-positive rate of 16. 60%. The two Springer Spaniels exhibited an equal ability to detect cancer patients with a sensitivity of 86. 54% and a false-positive rate of 20%. There was no statistically significant difference between the three dogs in detecting lung cancer(P =0. 994). Conclusion Olfactory detection of lung cancer by trained sniffer dogs may be used to assist clinical diagnosis andenhance diagnostic efficacy.