This semi-longitudinal investigation identified the chemistry topics that the majority of Irish chemistry pupils/students find difficult, from Junior Certificate level (age 15/16 years) right the way through to University level (age 18+). Pupils/students completed a five point, Likert-type questionnaire listing the topics covered in the different chemistry courses, which asked them whether they found each topic difficult or easy. They were also asked to identify which five topics they found most difficult, ranked 1 to 5. This paper highlights the topics that Irish pupils/students find difficult in chemistry. Topics identified by Irish students are similar to results of studies carried out in the UK by Ratcliffe and in Scotland by Johnstone. This study indicates that a number of topics ranked high in terms of perceived difficulty in both the Leaving Certificate chemistry pupils and University chemistry students lists. These topics were Volumetric Analysis Calculations, Redox Reactions and Concentration of Solutions. The persistence of these topics being seen as difficult throughout the pupils/students experience of chemistry indicates that problems associated with these topics have never truly been addressed. Other findings indicate that the mathematical ability of the pupils/students has an effect on the topics pupils/students chose as difficult or very difficult. (Contains 17 tables and 6 figures.)