Emap's share price rose 4% this morning to 872.5p, regaining the level it was at last July when it fell 15% on news that the company's revenues would slide.
The company said the executive search is underway and it reassured investors its full-year results will be in line with expectations of a 2% drop in revenues.
Cathcart said: "Tom has made a significant contribution to the company's development and leaves Emap positioned for growth in the new digital era. We wish him well for the future."
The internal favourite to succeed Moloney is Paul Keenan, the chief executive of Emap's consumer magazine division, who was last year handed additional responsibility for Emap's radio operations.
Moloney himself was appointed chief executive in January 2003 after climbing the Emap ladder via the consumer magazines division, having originally joined in 1981. He took over from Robin Miller who took over in the interim after Kevin Hand departed in 2001.
Another contender is Derek Carter, chief executive of the business publishing side of Emap, Emap Communications.
Moloney's four-year tenure began with him improving relations between the company and the City in the wake of its disastrous foray into the American magazine market with the acquisition of Petersen.
Under his watch, Emap carried out the acquisition of Scottish Radio Holdings for £391m in summer 2005 and of B2B fashion website Worth Global Style Network for £140m later that year. It also invested in new weekly consumer magazines, launching Zoo in 2005, Grazia in 2005 and First in 2006.
However, relations with the City started to sour as revenue growth levelled off and began to decline. The poor performance of the company's French consumer magazine division led to it being sold off in summer 2006 for £375m.
By 2006 it was evident that Emap's strong men's consumer magazine portfolio was in difficulty, with market leader FHM posting double-digit declines in circulation.
In February this year the company warned profits would be at the lower end of expectations, while rumours that headhunters were looking for Moloney's replacement led to the company issuing a statement to back him.
His last significant action was to enact a cost-cutting programme aimed at achieving £20m of annual savings and which involved a cull of all publisher and ad director roles on the consumer magazines.
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