Permanent missions were established in the 1961 Vienna Convention on Diplomatic Relations, which recognized that such practices contribute to the development of friendly relations among nations, irrespective of their differing constitutional and social systems. The United Nations is comprised of 193 Member States, of which 181 permanent missions of Member States are accredited to United Nations Office at Geneva. 

Operationally, permanent missions organize and coordinate their Member States participation in the work of the Organization. UN Geneva performs representation and liaison functions with accredited permanent missions and observer offices to facilitate and support their participation.

Non-member States, intergovernmental organizations and other entities, may also be invited to participate as observers in the work of the United Nations, and as such may maintain a presence in Geneva.

Diplomatic personnel working for these missions and observer offices are accorded certain rights, privileges and immunities as outlined in the Convention on the Privileges and Immunities of the United Nations. 

In each permanent mission a health attachés follow the health issues.

List of permanent missions is on this link : https://www.ungeneva.org/en/blue-book