Emergency services raced to the scene after the vehicles collided on the A83 near to Cairndow yesterday.
However, two passengers in the van, a 20-year-old and a 24-year-old, died at the scene.
The 63-year-old male driver of the van was taken to the Southern General Hospital in Glasgow, where he was treated for minor injuries.
The 24-year-old driver of the lorry was uninjured.
An investigation is underway into the incident, which happened at around 4.30pm.
Constable Alex Smith, from the road policing department at Dumbarton police office, is leading the inquiry.
He said today: "I would urge any witnesses to the crash, or anyone with information to contact the road policing department."