Chaviano was president of the Cuban National Council for Civil Rights when he was arrested in May 1994.
He was sentenced in secret by a military court in 1995 for revealing state secrets while documenting the cases of people who disappeared or died trying to leave Cuba on rafts.
Chaviano denied revealing state secrets and his supporters said no defence was presented during the trial.
The number of political prisoners in Cuba dropped from 283 to 246 in the first half of the year, the commission reported.
But the report also said the human rights situation had not improved since Fidel Castro, the ailing Cuban leader, handed over power to Raul Castro, his brother, more than a year ago.
The Cuban government denies there are political prisoners in Cuba and says dissidents are on the payroll of the United States.