In Europe, healthcare systems differ between countries and different factors may influence Chronic hepatitis B (CHB) treatment choices in different counties. This analysis from a prospective, longitudinal, non-interventional study in five EU countries aimed to explore determinants associated with treatment initiation or switch in patients with CHB. A total of 1267 adult patients with compensated CHB in Germany, France, Poland, Romania and Turkey were prospectively followed for up to 2years (March 2008-December 2010). Determinants of treatment initiation or switch were analysed using multivariate Cox proportional hazards regression. Median time since CHB diagnosis was 2.6 (0-37.7)years. Among 646 treatment-naive patients, the probability of treatment initiation during follow-up was higher: in Germany (P=0.0006), Poland (P<0.0001) and Romania (P=0.0004) compared with Turkey; in patients with alanine transaminase (ALT) 1-2xupper limit of normal (ULN) (P=0.0580) or >2xULN (P=0.0523) compared with ALT 1xULN; and in patients with hepatitis B virus (HBV) DNA 2000IU/mL (P<0.0001) compared with HBV DNA <2000IU/mL or undetectable. Among 567 treated patients, 87 switched treatment during follow-up. The probability of treatment switch was higher: in France (P=0.0029), Germany (P=0.0078) and Poland (P=0.0329) compared with Turkey; and in patients with HBV DNA <2000 (P<0.0001) or 2000IU/mL (P<0.0001), compared with undetectable. Viral load and ALT level were identified as the major drivers of treatment initiation. HBV DNA level was also a significant determinant of treatment switch. Results were statistically different across EU countries.