This thesis addresses various aspects of the role of competition between European honeybees and wild pollinators on pollinator community structure and pollination services. In experimental studies in flight cages, the presence of foraging honeybees led to a decrease in visitation rate of bumblebees and increased their flower handling time. The travelling rime that bumblebees spent flying between flowers showed a positive relationship with number of honeybees per flower. In a field study, the proximity to a honeybee apiary significantly decreased the abundance of different groups of pollinators. Species richness and diversity of wild pol1inators also declined with proximity to the honeybee apiary, except for bumblebees. Pollination service significantly declined with the increase in distance from the apiary. In a field study assessing the development of experimental bumblebee colonies, those located near the honeybee apiary produced fewer queens and smaller queens and males. The offspring sex-ratio was significantly more male-biased in colonies closer to the apiary, which is less costly, but may result in lower fitness depending on the population sex ratio. Average colony weight near the apiary was lower in one of the two years. Finally, in an experimental study of plant pollination success, I found that pollinator performance (in terms of pollen transferring and their contribution to seed set) depended on the plant species, as bumblebees were more efficient on oilseed rape than honeybees and hoverflies while they did not differ from honeybees in terms of field bean pollination and seed set. Together these studies support the idea that honeybees interfere with foraging activity of wild pollinators. For bumblebees, the presence of high density of honeybees can negatively affect colony fitness. For the plant species that I studied, there were clear differences in the quality of visits for pollination between the species. However, this did not lead to lower seed set, because honeybee numbers overcompensated for the lower numbers of wild pollinators