The Office's head office, horizontal services and four operational units are located in Brussels. There are two other units, one in Luxembourg and one in Ispra (Italy).

In all organisations, whether public or private, staffing matters are dealt with by internal departments. 

The Paymaster Office (PMO) administers the financial entitlements of the staff.

The PMO administers, calculates and pays the financial entitlements of the staff of the European Commission and certain other Community institutions and bodies. 
These individual entitlements are:

- salaries and allowances;
- reimbursement of experts and mission expenses;
- health insurance and accident cover;
- pensions;
- unemployment.