Current holders Hampshire Royals beat Derbyshire Phantoms on Monday to confirm their place in the Yorkshire Bank Pro40 last four, where they will face Glamorgan Dragons.
A 41-run win secured Hampshire top spot in Group B and therefore a home semi-final against the Welsh outfit, whose victory over Yorkshire Vikings saw them progress as the best-placed runner-up.
Defeated Twenty20 quarter-finalists Nottinghamshire Outlaws and Somerset Sabres have a second shot at claiming a limited-overs trophy this year and will meet in the other last-four clash.
A five-wicket win for Notts at Kent guaranteed that the fixture will be played at Trent Bridge, as Somerset finished with less points that the Midlands county despite overcoming Gloucestershire Gladiators on Monday.
The matches will be played on the weekend of September 7.