OBJECTIVES It is estimated that 30% of psoriasis (PSO) patients also develops psoriatic arthritis (PSA). This potential disease evolution brings along new symptoms such as swollen and painful joints  and mobility problems. Since both diseases are potentially degenerative, the aim of this study was to measure which group of patients (PSO or PSA) is willing to pay most out of pocket to avoid their health related quality of life (HRQoL) to worsen. METHODS RESULTS For both PSO (R² = 0,82) and PSA (R² = 0,86) monthly cost out of pocket (x-variable) was a good predictor of the proportion of patients that is willing to pay a certain amount out of pocket per month (y-variable). Regression models look as follows. For  PSO: y =0,77e^-0,005x for PSA: y = 0,86e^-0,007x