In China, lung cancer is the most common cancer with high mortality. While prior research suggests that health information scanning influences cancer screening within the general population, a deeper exploration of the underlying mechanisms is imperative. This study specifically targets smokers, aiming to investigate whether online health information scanning can effectively encourage lung cancer screening and elucidate the mechanisms driving this association. Data were extracted from a Chinese national survey conducted between January and September 2023, exclusively involving current smokers (N = 992). A moderated mediation model was employed to examine a cognitive-affective sequential chain of mediation through risk perceptions and cancer worry. Results showed that 99.1% of Chinese smokers reported online health information scanning, which possessed significant influence. Online health information scanning was positively associated with effective lung cancer screening among smokers directly (OR = 1.927, p < .01) and indirectly (OR = .065, p < .001). The perceived threat of smoking and cancer worry served as the cognitive and affective mediating mechanisms. Furthermore, a moderating effect of eHealth literacy was observed (OR = 6.292, p < .05). Smokers with higher eHealth literacy are more inclined to undergo effective lung cancer screening. Based on these findings, public health sectors should leverage online platforms to disseminate tailored cancer screening education and implement initiatives to enhance public eHealth literacy.