Although asthma and COPD alone are well known, the overlapping disease is less understood, according to University of Tasmania researcher Sukhwinder Sohal.

He said treating patients with symptoms of both diseases had been largely "by guess".

"Part of the problem is that clinicians don't know what the lung looks like in a patient who's got asthma plus ... COPD," he said.

"If you don't know what it looks like, you can't diagnose it, you can't properly treat it."

Dr Sohal's research, funded by the Clifford Craig Foundation, found ACOS patients had distinct airway changes to those with asthma or COPD alone.

"Once you know that these are the pathology features of this particular disease, then the therapy could be targeted," he said.

"It's going to inform clinical practice that this is [what] a lung looks like and clinicians can better treat these patients in our community, and also nationally, and also internationally as well."

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Prevalence of ACOS is high in Tasmania, and the state has some of the highest rates of asthma and smoking in Australia.

General practitioner Dr Jerome Muir Wilson, who runs the Launceston Respiratory Clinic, said getting the right diagnosis and treatment could help prevent infective exacerbation and hospitalisations.

"Where the diagnosis wasn't exactly clear ... often they'd be diagnosed with asthma or COPD, but sometimes it might be one or the other, or both," he said.

"On the ground, the treatments are similar, but subtly different, and the earlier you can treat any illness with the right path or therapy, the less long-term implications.

Dr Wilson said when people were misdiagnosed, they could end up with more infections and scars.