Background Previous research shows that pictorial warning messages (PWMs) for tobacco cigarettes increase quit attempts and smoking-related knowledge. However, few studies have investigated what specific features within PWMs are most effective. The current study sought to examine the specific features of PWMs associated with effectiveness using four outcome measures as indicators.

Method A sample of n=319 PWMs was collected and underwent systematic content analysis on 48 different content features. A sample of n=1392 current smokers each rated a subset of the labels on perceived effectiveness, negative emotional engagement, intentions to enact avoidance behaviours and intentions to forego a cigarette. Multilevel random-effects models were fitted with all coded content features and each of the outcome measures.

Results Analysis across all four outcome measures shows that PWMs depicting diseased and damaged body parts and employing a testimonial format were most effective. Additional mediation analysis showed that image-level negative emotionality partially mediated the relationship between PWM features and perceived effectiveness.

Conclusion The effectiveness of graphic imagery, testimonials and images that elicit negative emotions provides guidance for researchers as well as for future implementation of more effective PWMs.