His main interest is with socioeconomic, geographic and ethnic inequalities in health and smoking, with a particular interest in the relationship with tobacco control policies at local and national levels. He has led European research projects on inequalities in youth smoking, with the aim to identify new opportunities for smoking prevention (the SILNE projects). Within the Netherlands, he coordinates research on smoke-free environments (including school, hospital and sports premises) and the tobacco retail environment (including tobacco display bans and measures to reduce the number of outlets). In his research, he combines quantitative, epidemiological approaches with qualitative methods based on in-depth interviews. He co-published around 200 articles in peer-reviewed journals on the topics of smoking and tobacco control.