As of April 15, 1962, per John XXIII’s (#262) Cum gravissima motu proprio, all cardinals are required to be consecrated as bishops (unless an explicit exception is granted by the
pope, typically on the grounds of advanced age; i.e., approaching or over 80).
This requirement for episcopal consecration is now embodied in Canon 351 §1 of the 1983 Code of Canon Law.
Since this requirement went into effect, as of 1962, about eleven cardinals were granted exceptions. Of these, American Cardinal Deacon Avery Dulles, a Jesuit, created in 2001, who died on December 12, 2008, age 90, probably been the best known. Czechoslovakian Cardinal Tomáš Špidlík, another Jesuit, who died on April 16, 2010, also at 90 was another. He was created a cardinal deacon in 2003.
The current cardinals who are not bishops are:
1. Italian Cardinal Deacon Roberto Tucci, a Jesuit, a one time Director General of Radio Vatican, created on February 21, 2001, two months ahead of his 8oth birthday.
2. French Cardinal Deacon Albert Vanhoye, a Jesuit and academic, created on March 24, 2006, at the age of 82.
3. Spanish Cardinal Deacon Urbano Navarrete Cortés, also another Jesuit and academic, created on November 24, 2007, at the age of 87.