Prosecutors originally sought life sentences for at least a dozen of the 80 defendants, but no such sentences were among those announced Monday.
Opposition political party leader Hector Palacios, among those originally recommended for a life sentence, received a 25-year sentence, said his wife, Gisela Delgado.
"This is an injustice," Delgado said after leaving the courthouse. "We are as Cuban as members of the Communist Party."
Independent journalist Raul Rivero received the 20-year sentence sought by prosecutors, family members said.
The communist government accuses the dissidents of being in the pay of Washington and collaborating with U.S. diplomats here to harm Cuba and its economy.
The last of the summary trials, which began Thursday, were expected to end Monday, with all sentences to come before the end of this week.
Among those tried Monday was Dr. Oscar Elias Biscet, a physician who has been held since being arrested during a December protest. Prosecutors sought a 25-year sentence.
Biscet was released from prison in October after serving nearly three years for displaying three national flags upside down in an act of civil disobedience.
The crackdown has been condemned by international human rights groups and press organizations. The U.S. State Department called the proceedings a "kangaroo court."
Those arrested in last month's crackdown include more than two dozen journalists, leaders of independent labor unions and opposition political parties, and pro-democracy activists involved in a reform effort known as the Varela Project.
The crackdown ended several years of relative government tolerance for the opposition. It began when Cuban officials criticized the head of the American mission in Havana, James Cason, for actively supporting the island's opposition.
By Anita Snow