Two papal conclaves were held in 1503.
The first conclave was held following the death of Pope Alexander VI on August 18, 1503. This conclave lasted from September 16, 1503 to September 22, 1503 and ended in the election of Cardinal Francesco Todeschini Piccolomini, who took the name of Pope Pius III.
The second conclave followed the death of Pope Pius III on October 18, 1503. This conclave lasted from October 31, 1503 to November 1, 1503 and ended in the election of Cardinal Giuliano della Rovere, who took the name of Pope Julius II.
Participants in the Conclaves of 1503
The following table lists all cardinals eligible to vote in the papal conclaves of 1503 and indicates which conclaves each cardinal actually participated in.
References
Cardinal electors for the 1503 papal conclaves Wikipedia(Text) CC BY-SA