Patient-relevant outcome measurement has finally hit prime time. Health care systems are latterly realising that clinical and care decision-making needs to incorporate an understanding of the patients’ expectations, experiences, hopes, and fears. Only through the systematic capture of patient-relevant data can we tailor healthcare decision-making to end users of healthcare, empowering them to engage with the system in a way that maximises both their health and their well-being. This is a big step forward in the principles of evidence-based medicine. Now, we need patient reported outcome measures (PROMs) and patient-reported experience measures (PREMs) that allow us to collect information from patients in a systematic and standardized way to ensure consistency and continuity of care, and against which to appraise treatment options. Although PREMs are a relatively new consideration, PROMs have been around for many years. In the past decade PROMs have routinely been included in drug development trials to evaluate hypothesised benefits afforded by medications with improved pharmacodynamics and pharmacokinetic properties and which are administered in novel ways, at reduced frequencies. The problem is that there are literally hundreds of PROMs vying for attention. They are not all created equally and we need to decide which are best. To do this we must disentangle the “what” and the “why” from the “how”. A PROM is a measurement tool; one which must be reliable and valid if it is to generate interpretable data. But it is the underlying concept of interest which needs to be given greater emphasis. For example, there are numerous PROMs which claim to measure quality of life in diabetes; but what aspects of life are we particularly interested in, and why? More than 10 PROMs have been developed to evaluate psychological well-being, but again this is a multidimensional construct. What, specifically are we interested in, and why? Knowing this will determine which of these PROMs, if any, is appropriate. This talk will aim to help delegates to ask the right questions in order to select the best PROMs or PREMs to evaluate safety and efficacy of treatments and healthcare decisions, and ultimately enhance patient care.