The 86-year-old was hurt in Cleckheaton, West Yorkshire, just before 2pm yesterday (Friday), police said.
A West Yorkshire Police spokesperson said: "Bradford Roads Policing Officers would like to speak with anyone who witnessed the incident which took place at about 1.57pm on Friday, August 24.
It occurred after a Lexmoto 125CC scooter was in collision with an 86-year-old man on Brooke Street, Cleckheaton.
"The 86-year-old was in the road when the collision occurred.
"The man suffered a head injury and was taken to Pinderfields Hospital, where he is in a stable condition today."
Witnesses should call police on 101 with the log number 943 of August 24.