In 1928, Mater Public Hospital installed Queensland’s first deep x-ray therapy machine to treat cancer patients. In 1930, the new unit treated 94 cancer patients by radiation therapy and a further 122 by deep x-ray. This same year, the first Mater Pharmacy opened. At the time, Queensland law required pharmacies to be owned by pharmacists so the pharmacy was registered in the secular name of Sister Mercia Mary Higgins—the Sisters’ only qualified pharmacist.
On 10 May 1931, almost five years to the day after the foundation stone was laid, Mater Children’s Hospital officially opened, dedicated as a memorial to Mother Patrick Potter. On 6 July 1931, Mater Children's Hospital opened its doors to patients. Every bed was immediately occupied, and more than 8200 patients were treated in its first year of operation.
In 1937, the Mater Private Hospital eastern wing was officially opened and blessed by Archbishop of Brisbane James Duhig. The following year, in 1938, Brisbane Lawyer, John P Kelly, was appointed as Chairman of the newly established Mater Public Hospital Medical Board. This was a position he would hold for more than 40 years.