Psychology uses theory supported by empirical evidence to accumulate generalisable knowledge and learn from various contexts. Two commonly used theories are the Theory of Planned Behaviour (TPB) and Common-Sense Self Regulation Model (CS-SRM). Possible limitations in previous studies using these theories have been identified: (1) TPB studies focus upon one specified behaviour and ignore behavioural alternatives; (2) the CS-SRM is routinely not fully operationalised. This research aimed to develop an ‘extended TPB’ assessing ‘intention choice’ (where participants report their intended course of action regarding one or more specified behavioural alternatives) and to operationalise the CS-SRM more fully than is usually reported. The context was people with urological cancer. Methods: Three studies were conducted: (1) CS-SRM-based longitudinal study of people with urological cancer (n=172) to predict anxiety and depression; (2) Extended-TPB-based prospective study of men with localised prostate cancer (n=35) using both between- and within-person approaches to explore intention choice with respect to treatment; (3) Extended-TPB-based before-after study of medical students (n=93) to evaluate the effects of teaching on simulated communication behaviour. Results: (1) Anxiety and depression at Time 2 were predicted by number of information sources reported at Time 1 after controlling for baseline anxiety and depression; (2) TPB constructs were consistent with intention choice and intention choice was consistent with actual treatment. Within-persons, the model could not identify men who later reported poor outcomes; (3) All TPB-related cognitions changed between Time 1 and Time 2 but simulated behaviour scores did not change. Discussion: Relationships between the TPB constructs both between- and within-persons were consistent with actual treatment. The extended TPB measures were sensitive to change when behavioural alternatives were assessed. The CS-SRM was operationalised beyond illness representations. Conclusions: It was feasible to apply both the extended TPB (between- and within-persons) and CS-SRM in this context.