Lorimer joined Manchester Central in March 2007. Previous roles have included event director of International Confex, which she took on in 2001, before leaving in 2003.
A statement from Manchester Central said: "Paula led the sales team through a period of significant growth and transition, following completion of the £30m redevelopment, and successfully attracted a number of prestigious events to the venue.
"Manchester Central takes this opportunity to thank Paula for the valued contribution she made during her tenure, and wish her every success for the future."
Elizabeth Faulkner has taken on the newly created role of assistant CEO – sales, marketing and communications at Manchester Central, following Lorimer's departure.
Faulkner has worked at the venue for two years as director of marketing and communications.
Faulkner said: "Manchester Central has built up an enviable reputation for hosting some of the world's best events. Over the coming weeks we will be developing our team, with the addition of new sales professionals, to build on that success."