PWSAI was started by parents in the late 1980s as a support group for people with PWS and their families in Ireland. It formalised its status in 2002 when it became a company limited by guarantee. It has retained company status since and in 2012 changed its memorandum and articles of association to allow it to begin formally registering members. PWSAI has a full-time Development Officer whose role is fully funded and it also relies on volunteers for other  activities. It is audited annually and submits annual accounts to the Companies Office.

Mission, Vision and Values