Reading's first league win since Boxing Day reignited their promotion push as the Royals moved three points clear of West Ham and the chasing pack.
Reading served notice of intent inside five minutes when West Ham could only half clear a corner into the path of Ricky Newman whose dipping volley was finger-tipped on to a post by Stephen Bywater.
That early chance exposed West Ham's vulnerability at set-pieces and Reading took advantage as they opened the scoring on 13 minutes.
Malky Mackay was adjudged to have fouled Dean Morgan on the left edge of the penalty area and Nicky Shorey's inviting free-kick was headed home at the far post by Kitson.
The striker, who scored twice in the corresponding fixture last season, has been conspicuous by his absence for Reading in recent months.
Their 11-game winless run, stretching back to Boxing Day, coincided with Kitson's two-month lay-off with a knee injury.
And Reading's top scorer was clearly hungry to make up for lost time as he doubled Reading's advantage with another header on 27 minutes.
Again it was a set-piece that undid West Ham as Kitson won a corner off Bywater and then arrived at the back post again to head home after Morgan had flicked on Shorey's corner.
West Ham were all over the place, and although Marlon Harewood twice threatened early in the second half, the outstanding Kitson put the Hammers out of their misery before the hour was up.
Morgan's threatening run and fierce shot was beaten out by Bywater, who then recovered well to block Kitson's follow-up, but there was nothing he could do to keep out Kitson's second attempt as the striker fizzed a shot on the turn between two defenders on the line.
Bywater then saved twice from Kitson again, a header from a Glen Little corner and then a low shot after Morgan had flicked a header into his path.
But by then the damage had been done and to describe substitute Teddy Sheringham's late reply as a consolation would be inaccurate as the disgruntled Hammers fans had been venting their disapproval long before West Ham's third successive defeat was confirmed.