Shannon’s dreams of a possible AIB League and Cup double were dashed at Deramore Park as Belfast Harlequins edged them 32-28 in a seven-try thriller.
‘Quins won through to the April 14 cup final as centre Darren Cave, hooker Stuart Philpott, scrum half Paul Marshall and winger Paul McKenzie crossed for tries.
Ireland Under-20 international Niall O’Connor kicked 12 points as Andy Ward’s side did just enough to book a decider with Garryowen.
A 35th-minute try from captain Colm McMahon drew Shannon level at 17-17 for the interval. But scores from Marshall (52 minutes) and McKenzie (62) were decisive.
Scorers: Harlequins: Tries: Darren Cave, Stuart Philpott, Paul Marshall, Paul McKenzie; Cons: Niall O’Connor 3; Pens: O’Connor 2. Shannon: Tries: Frankie McNamara, Colm McMahon, Les Hogan; Cons: Andrew Thompson 2; Pens: Thompson 3