Police are trying to work out how a man found unconscious in his Scarborough home this week suffered his injuries.

Mirrabooka Detectives are investigating the incdient after the 47-year-old man was found inside his Sackville Terrace home injured and unconscious about 3pm on Tuesday.

He was taken by ambulance to Royal Perth Hospital and is in a critical but stable condition.

Detectives are establishing a timeline of the man's movements between 7pm on Sunday
and 3pm Tuesday.

They would like to speak to anyone who was in or driving in the area of Sackville Terrace between Duke Street and Grand Promenade who heard or saw any disturbances or suspicious activity.

Police are also asking anyone who was in the area during the above times who has dash-cam footage or CCTV from their homes to come forward.

Anyone with information should call Crime Stoppers on 1800 333 000 or make a report online at www.crimestopperswa.com.au.