Objective: Nasopharyngeal cancer (NPC) risk factors caused by lifestyle choices are substantial yet avoidable. Using the Health Belief Model as a conceptual framework, this study develops and validates a questionnaire to predict smokers' intentions to quit in Sarawak, Malaysia (HBM).

Design: A cross sectional study.

Setting: Urban and suburban areas in Sarawak, Malaysia.

Participants: Following a thorough literature study, the preliminary items for the instrument were created. Prior to beginning the content validity by a panel of 10 experts, the instrument was translated into the Malay language utilising the forward-backwards approach. 10 smokers carried out face validity in both quantitative and qualitative ways. Exploratory factor analysis (EFA) and confirmatory factor analysis (CFA) were used to assess the instrument's concept validity. Phase 1 of the EFA involved 100 smokers, whereas phase 2 of the CFA involved 171 smokers. Cronbach's alpha coefficients were used to measure internal consistency and assess reliability.

Results: The factor loading of each item remained within the acceptable threshold in the exploratory stage. The final revised CFA yielded the following model fit indices that suitably fitted the seven-factor model: Chi Square: 641.705; df= 500; P< 0.001; CFI = 0.953; TLI: 0.948; RMSEA= 0.041. With the exception of one pairwise construct, satisfactory convergent validity and divergent validity were demonstrated. Phases 1 and 2 both have Cronbach's alpha values over 0.7, suggesting acceptable internal reliability.

Conclusions: The study confirmed the validity and reliability of the instrument in predicting smokers' tendency to adopt healthy behaviour of smoking cessation to lower risk of developing cancer. The instrument consists of 34 items, dividing into two sections: 6 HBM components and health behavioural intention. The instrument is regarded as innovation and can be applicable in other smoking-related malignancies in different susceptible populations and geographical locations.

Following face and content validation, 100 and 171 local smokers took part in phases 1 and 2, respectively, using a convenience sampling appraoch. Eight well-trained research assistants helped with the data collecting. Prior to obtaining questionnaires, participants were informed about the purpose and design of the study, as well as its advantages and concerns. There was no danger and participation in this study was entirely voluntary.

Microsoft Excel was used to process the data before SPSS 26.0 and AMOS 24.0 were used to analyse it. Internal consistency was assessed using Cronbach's alpha values. The construct validity of each component was examined using exploratory factor analysis (EFA) and confirmatory factor analysis (CFA). Particularly, EFA and CFA were assessed in phases 1 and 2, respectively. Statistical significance was determined by a p-value of less than 0.05.