The Swedish building sector is rapidly changing. While construction rates are the highest they have been for 50 years, the sector is under- going structural transformation as large parts of production are externalised and both major and minor firms rely heavily on subcontractors. Additionally, the sector increasingly makes use of posted workers from predominantly Central and Eastern Europe. Structures of subcontracting analyses the augmented use of subcon- tractors in the Swedish building sector, with the point of departure in a qualitative study of two building companies. Building on a theoretical tradition of sociology of work and organisations, the study identifies a variety of ways in which work is organised through subcontractors. A key contribution of this study is the conceptualisation of new forms of subcontracting arrangements as masked staffing. Through the use of masked staffing, this dissertation shows how subcontractors are hired according to principles of staffing rather than external business relations, allowing firms to effectively sidestep employer responsibility while at the same time maintaining control of the labour process.