Cameron and Putin met on the sidelines of the G20 summit in Saint Petersburg after discussing the Syrian crisis over dinner with other world leaders and watching a cultural show that ended around 2:00 AM (2200 GMT).
"The sides have once again exchanged views regarding the situation in Syria," Kremlin spokesman Dmitry Peskov told Russian news agencies.
The Russian president and British prime minister also "confirmed their intentions to continue working on developing cooperation on a wide variety of issues," Peskov said.