The Bluebirds will be the happier of the two sides heading into next week's second leg in Wales but they look set to be without Craig Bellamy.
The on-loan Manchester City striker lasted just 17 minutes before going off injured but Dave Jones' side shook off the loss to limit the Royals in a poor game.
An all-Welsh final at Wembley now looks favourite after Swansea held Nottingham Forest to another stalemate on Thursday night.
Reading boss Brian McDermott - who played for Cardiff - saw his side fail to reach their usual tempo and they must now pull off a fine performance in the second leg to keep their hopes alive.
Bellamy posed the first threat after 11 minutes, racing onto Peter Whittingham's magnificent through ball to fire in a cross-shot which Royals goalkeeper Adam Federici had to tip away for a corner.
The Australian was in action again from the following set-piece to palm away a Jay Bothroyd strike but Bellamy was soon back in the stand after appearing to clutch his hamstring when chasing down a clearance.
Jones turned to Michael Chopra as his replacement and he was soon poleaxed by Jobi McAnuff as the game began to turn niggly.
Both sides were fined by the Football Association after a brawl in the 2-2 draw in Wales in February and McAnuff did little to ease tensions when he left his foot in after a high challenge and was rightfully booked by referee Mark Halsey.
Reading winger Hal Robson-Kanu saw an improvised back heel deflected wide as the hosts ended the first half with a spell of pressure but Stephen Bywater remained untroubled in the Cardiff goal.
Chopra was then lucky to escape a caution for a wild challenge on Jem Karacan before Reading skipper Matt Mills was booked for hacking down Kevin McNaughton.
McNaughton pulled off a fine challenge to prevent Robson-Kanu from streaking clear seconds before the break as the sides went in goalless.
Mills came close in the opening minutes of the second half when Shane Long headed an Ian Harte corner back across goal but the former Manchester City defender was unable to divert the ball on target.
Bothroyd then went down in a heap after Long trod on his foot but after treatment he was able to continue.
Whittingham sent a 25-yard drive just wide of Federici's left corner despite being hampered by referee Halsey as the visitors began to win control in midfield.
Federici then flapped at a deep free-kick but escaped as Jay Emmanuel-Thomas' flick-on evaded Bothroyd and neither side could fashion another opportunity as a disappointing evening came to a close.