BMW-Sauber's Pole was clearly knocked unconscious when his car slammed into a concrete wall at full speed after a dice with Jarno Trulli.
The destroyed single seater then rolled several teams before coming to a rest on its side at the chicane, and he was attended to by doctors for several minutes before being taken to the medical centre with no word about his condition.
A team spokesman later confirmed that Kubica is "stable", while his manager reported that Robert was moving his arms and legs without problem.
He has been taken to hospital for further checks.
On track, the 2007 Canadian grand prix was hectic and incident-packed, with the safety car required multiple times.
Felipe Massa and Giancarlo Fisichella were disqualified for speeding through red lights at the end of the pitlane, while world champion Fernando Alonso - driving a scruffy race in the sister McLaren - had to serve a stop-go penalty for pitting when the pit lane was closed.
The Spaniard finished just seventh, allowing Hamilton to take the lead in the drivers' championship by eight points. (GMM)
1. Lewis Hamilton (McLaren)
2. Nick Heidfeld (BMW)
3. Alexander Wurz (Williams)
4. Heikki Kovalainen (Renault)
5. Kimi Raikkonen (Ferrari)
6. Takuma Sato (Super Aguri)
7. Fernando Alonso ( McLaren)
8. Ralf Schumacher (Toyota)