Conversion into housing is a way of adapting and reusing vacant office buildings. Former research has shown possibilities for this type of conversion, and has delivered instruments for determining the conversion potential of vacant offices. While adaptation and renovation of outdated offices can prove to be a successful real estate strategy, conversions into housing still take place only on a small scale. There are several reasons for this, like uncertainty about financial feasibility, and little knowledge about the opportunities and risks of building conversions. This paper reveals drivers for office-to-housing conversions and conversion opportunities and risks, based on a review of international literature and a cross-case study of 15 buildings in the Netherlands which were converted from offices to housing. The findings show that various legal, financial, technical, functional and architectonic issues define the opportunities and risks of building conversions. These insights can be used to support decision making on how to deal with vacant office buildings.