Cadet units are for young people aged between 10 and 21, although most become adult members at the age of 18. The first unit was established in 1922 and since then the Cadets have gone from strength to strength, with the youth section of the organisation making up over two thirds of the current membership in Wales.

Life in the Cadets is about fun, adventure and community. Participants can learn and develop skills in a wide range of subjects which fall into the three main areas of first aid training, operations and care. Topics such as first aid, photography, sports, fire prevention and other life skills are available. As a uniform organisation the Cadets are also taught Drill, Salute and Discipline.

In the thirty years since Aberdare Cadets was formed, it has helped members progress into careers as doctors, nurses and teachers. The unit has been successful in many challenges and competitions with members participating in the Duke of Edinburgh's Award scheme and being presented with the Grand Prior Award - the highest honour which can be given to a Cadet by St John Ambulance.