Purpose: This paper investigates factors that influence effective workplace designs for knowledge workers. Design/methodology/approach: During spring 2016, the employees in a large Norwegian institution for research and higher education, a large consultancy company and a medium size consultancy company (in total 4367 employees) received invitations to participate in an anonymous online survey about workplaces and facilities. 1670 employees (38.2 per cent response rate) answered the survey. The data have been analysed with IBM SPSS version 23, among others through use of exploratory factor analysis and two-way ANOVA. Findings: Most respondents at the institution for research and higher education have cell offices. Most respondents in the two consultancy companies have open and flexible offices. This study indicates the respondents' preferences or perception of their workstation and workplace's fit for their tasks is affected both by the respondents' type of office and how much time they spend at their workstation during the week. Practical implications: The present research indicates that facility managers and others responsible for office and workplace design are advised to take the employees' work patterns into consideration when designing workplaces and providing offices and workstations to their end-users. The present research also indicates that employees require different kinds of support facilities depending on what kind of offices and workplaces they have. Originality/value: This is a large N empirical study among knowledge workers in three organisations, one public administration and two private enterprises. The present research indicates that provision of offices and workstations with supporting facilities should be differentiated according to the end-users' work tasks and work patterns.