Four people were in a red Vauxhall Corsa that lost control, left the carriageway and collided with a white Volkswagen Caddy van.
Hampshire police are appealing for witnesses following the incident that happened yesterday in Alton, on the B3006, Selborne Road, at 8.30pm.
A 17-year-old girl and two men, aged 18, were taken to hospital to be treated for serious and possibly life-threatening injuries.
The driver of the Corsa, an 18-year-old man, was also rushed to hospital and treated for his injuries, though they are not currently considered serious.
A 26-year-old man, who was driving the VW van, also sustained minor injuries.
Officers are turning to the public for any information that may assist the investigation.People who were on the road at the time, or have dash cam footage of the crash, are asked to phone 101, quoting the reference number 44210471336, or Op Export.
Alternatively, witnesses can call Crimestoppers anonymously on 0800 555 111.