This chapter presents empirical data from over 1,400 adult diagnostic assessments conducted over a 10-year period. It demonstrates that dyslexia persists into adulthood and is characterised by persistent cognitive-processing weaknesses – most notably in working memory. The assessments were carried out using a structured protocol that includes cognitive tests (primarily the WAIS-IV), rapid-naming measures, and targeted literacy evaluations. The authors emphasise that diagnostic assessments should not merely assign labels but provide meaningful explanations that foster understanding and self-advocacy. They criticise checklist-style assessments and instead advocate for a parsimonious, individualised approach that respects the person’s reported challenges. Importantly, the data reveals consistent patterns: while many adults with dyslexia demonstrate strengths in verbal and non-verbal reasoning, they also show notable discrepancies in working memory and processing speed. These differences help to explain functional difficulties and inform targeted strategies. The chapter reinforces the importance of ipsative analysis – comparing a person’s abilities against themselves – to identify meaningful discrepancies and promote effective support. Overall, it positions cognitive testing as a crucial tool for not only diagnosis but also empowering individuals to understand and navigate their difficulties.