The top six placed teams from the top-tier levelGreek Basket League2016–17 season, gained an automatic bye to the 2017–18 Greek Cup quarterfinals. While the eight lower placed teams from the 2016–17 Greek Basket League season; along with all of the teams from the 2nd-tier level Greek A2 Basket League2017–18 season, and the 3rd-tier level Greek B Basket League 2017–18 season, play in preliminary rounds, competing for the other two quarterfinals places. The quarterfinals and onward rounds are played under a single elimination format.