A prominent Sydney surgeon who rushed operations on two patients who died has been deregistered for one year.

Dr William Mooney also was found to have had a relationship with a third patient and lied about his failure to attend a drug test.

The ear nose and throat surgeon had submitted the appropriate penalty would be a severe reprimand with conditions imposed on his registration.

Or if a period of suspension was deemed necessary, he said three months would be appropriate and sufficient

But the NSW Civil and Administrative Tribunal on Thursday agreed with the Health Care Complaints Commission which submitted his registration should be cancelled for 12 months.

"This is not a situation where a practitioner has failed to act in accordance with expected standards or depart from ethical standards on one occasion, or in respect of one course of conduct," it said.

"Dr Mooney has committed acts which are egregious departures from proper standards across a broad range of duties which a doctor owes to his patients and the public."

He previously was found guilty of professional misconduct and unsatisfactory conduct.

Patient A died in March 2018 after consulting Dr Mooney to fix his snoring.

An expert found he took an "astonishingly short" time to operate, suggesting "little time could have been spent on achieving control of the brisk arterial bleeding which had occurred".

Dr Mooney did not review Patient A over the next two days when he knew he had bled during the operation, but checked up via phone before his release.

He vomited blood from his nose and mouth and tried emergency contact numbers given by Dr Mooney but nobody answered, and was rushed to hospital.

He underwent emergency surgery for a recurrent haemorrhage, but had a heart attack during the operation and died later without regaining consciousness.

Patient B was 41 in 2017 when he sought more sinus treatment from Dr Mooney, who was found to have left a very short time for a complex procedure.

While operating, he penetrated the bone below the brain and disrupted an artery causing bleeding into the right frontal lobe.

The patient later died without regaining consciousness.

Dr Mooney also was found to have lied about a personal relationship, of more than two years, the 47-year-old had with a young vulnerable patient.

He also inappropriately prescribed her a weight loss medication when he should have known she had a longstanding eating disorder.

Dr Mooney also lied about complying with hair drug screening after avoiding tests due to "illness", and giving himself a "buzzcut," among other measures.

The tribunal accepted he was remorseful for his role in the two deaths and had made changes to address the shortcomings in his practice and operation procedures.

But it placed less weight on his stated insight and remorse in relation to the boundary violation with patient C, and his breaching of conditions and misleading the authorities.

Evidence was given of his current pro bono work for the Aboriginal and Torres Strait Islands ENT Committee and for a clinic for facial injury treatment following domestic violence.