Volcanoes exhibit similarities and differences in the chemistry, size and style of their eruptions. Understanding why the eruptive activity of two or more volcanoes is similar or different can provide insights into how local or regional processes control the accumulation and eruption of magma, as well as an understanding of the potential volcanic hazard. However, the comparison of eruptive activity between volcanoes is complicated by the fact that records of eruptions are often sparse and contain few observations. Volcanoes can remain dormant and not erupt for many decades, centuries or even millennia, making it difficult to compare chemical or physical parameters, as each individual record will inevitably be a subset of the volcano’s total history, and it may not necessarily represent all possible eruptive scenarios or states of activity. The chemistry, size and style of eruptive activity that is recorded will depend on the nature of observations collected from fieldwork and historical eruptions, as well as on how the magmatic system has evolved over time. The aim of this session is to bring together volcanologists to discuss what data can be used to best compare eruptive activity between volcanoes, how to identify groups of volcanoes that are similar, how best to characterise chemical and physical parameters to recognise differences between individual volcanoes or groups of volcanoes, and to examine the insights that these observations provide in understanding local and regional magmatic processes across a range of timescales.