The committee said governments in the 13 countries have consistently failed to solve murders where journalists were targeted from 1998 through 2007.
There are at least 199 unsolved murders in these countries during that period.
The victims include well known investigative reporters Anna Politkovskaya in Russia and Guillermo Bravo Vega in Colombia, Al-Arabiya correspondent Atwar Bahjat in Iraq, and kidnapped Pakistani reporter Hayatullah Khan, it said.
The new Impunity Index, released by the committee in advance of World Press Freedom Day on Saturday, includes six countries from South Asia - Sri Lanka, Afghanistan, Nepal, Bangladesh, Pakistan and India.
The countries with the worst records for impunity - Iraq, Sierra Leone and Somalia - have been mired in conflict, but the committee said most countries on the list are not at war and have law enforcement agencies. Yet, it said, journalists are regularly targeted for murder and no one is held accountable.
"Every time a journalist is murdered and the killer is allowed to walk free it sends a terrible signal to the press and to others who would harm journalists," said Joel Simon, the committee's executive director. "The governments on this list simply must do more to demonstrate a real commitment to a free press. Lip service won't help save journalists' lives."
"We are calling for action: thorough investigations and vigorous prosecutions in all journalist homicides," he said.