Intermediate results from an ongoing health technology assessment exercise of a simulation model of paediatric cardiomyopathy are reported. Comprehensive data on paediatric cardiomyopathy/heart failure, treatment options, incidence and prevalence, prognoses for different outcomes to be expected were collected. Based on this knowledge, a detailed clinical pathway model was developed and validated against the clinical workflow in a tertiary paediatric care hospital. It combines three disease stages and various treatment options with estimates of the probabilities of a child moving from one stage to another. To reflect the complexity of initial decision taking by clinicians, a three-stage Markov model was combined with a decision tree approach – a Markov decision process. A Markov Chain simulation tool was applied to compare estimates of transition probabilities and cost data of present standard of care treatment options for a cohort of children over ten years with expected improvements from using a clinical decision support tool based on the disease model under development. Early results indicate a slight increase of overall costs resulting from the extra cost of using such a tool in spite of some savings to be expected from improved care. However, the intangible benefits in life years saved of severely ill children and the improvement in QoL to be expected for moderately ill ones should more than compensate for this.