"We are friends, we are allies, we're colleagues," Cameron told a committee hearing at the Houses of Parliament in London.
"We've sent British planes to do the Baltic Air Policing, we work very closely with their intelligence and security services and very fruitfully too.
"They know that in Britain they've got a very strong friend... if you talk to the Latvian, Lithuanian or Estonian leaders, you'll hear that pretty strongly."
Asked if NATO would intervene if armed militias started operating in border areas of the Baltic states, Cameron replied: "We are committed to their collective defense and so where they are being destabilized we would intervene and help them with their stability."
"I think we need to do more, frankly, in the area of information. One of the complaints we get from the Baltic states is there is nothing to counter the deluge of Russian-paid and backed media spreading disinformation," he said.
"We have got to recognize one of the strengths we have got as a country, although we don’t always necessarily see it this way, is that we have a very strong and impartial media. We have a wonderful brand in the BBC known for its impartial views.
"We should be supporting the BBC to provide news services and news channels where people otherwise are getting a diet of Russian disinformation," the premier said.
"The Baltic states feel this pressure very greatly and they don't always feel the rest of Europe understands them... they are subject to a lot of destabilization and they want their NATO friends and partners to understand that," Cameron explained.
"We're doing a lot to reassure them that they are full members of NATO and get NATO protection in every way when they face these struggles."
During the session, Cameron also said Britiain would be sending military instructors to help train the Ukrainian army and refused to rule out sending other forms of aid, including weapons, in future if the situation continues to deteriorate.
The full committee session featuring Cameron can be viewed below with questions about the Baltics starting from 7 minutes in (Microsoft Silverlight required).