<p>It has been argued that engaging a wide range of stakeholders in regulatory policymaking could enhance its legitimacy, quality, and acceptability. Open consultations are the only venue that theoretically allows the participation of those affected by policy proposals or those with a special position in relation to them. We examine the participation of all stakeholder types in open consultations, including organized and non-organized interests, across policy areas and time in Finland, a country with a neo-corporatist background. Our novel dataset consists of over 16,000 written statements submitted in nearly 500 open consultations over three years (2013, 2017, and 2021). We study the level of diversity among stakeholder types using the Herfindahl–Hirschman index while also discussing the balance of their participation in relation to the policy areas in which their engagement occurs. Our findings reveal that organized interests are particularly active compared to non-organized actors, although we note some increase in the engagement of companies over the years. The overall level of stakeholder diversity reflects moderate concentration, but it varies considerably across policy areas. We suggest that occasional high concentration in engagement does not necessarily indicate imbalance, as the policy issue itself determines whose involvement is most relevant.</p>