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* Ad group shares up 4.5 pct, best CAC 40 index performer
* Internal reorganisation, Sapient drive performance
* Loss of large accounts in 2015 to be felt in Q3
* Successor of CEO Levy likely to be chosen internally (Recasts story, adds details)
By Mathieu Rosemain and Gwénaëlle Barzic
PARIS, July 21 (Reuters) - France's Publicis impressed investors on Thursday with quarterly figures thatflagged the success of a sweeping reorganisation and theintegration of its last big acquisition in the United States.
Despite the expected departure in 2017 of Maurice Levy, theCEO credited with the turnaround, shares in the world'sthird-largest advertising group were at an 11-month high at 1130GMT, rising 4.5 percent to 67 euros.
Second-quarter sales rose 2.7 percent on an organic basis to2.46 billion euros ($2.71 billion), beating a Reuters poll of1.72 percent organic growth for the period.
Publicis called 2016 a year of transition when it reported2015 results, as it digests the $3.7 billion acquisition ofU.S.-based digital business Sapient and reorganises itsbusinesses to foster greater collaboration between the manyagencies it has bought over the years.
The group is already attracting new clients such asGlaxoSmithKline and Asda, it said on Thursday.
The financial benefits will be seen as soon as 2017,Publicis said, while the integration of Sapient helped boostrevenue in the digital business by 6.3 percent in the firsthalf.
Chief Executive Officer Levy, who has led the company since1987, said the reorganisation had been one of his toughestchallenges.
He confirmed his successor as CEO will be presented by theboard between December 2016 and February 2017. Publicis' boardis looking at internal candidates only so far, he said.
He also said that the loss of large media accounts in 2015in the United States, Publicis' top market, will likely have a"significant impact" in the current quarter. These accountsincluded Procter & Gamble, Coca Cola, Mondelez et GeneralMills.
Omnicom said last week that its second-quarter organic salesgrowth was 3.4 percent. WPP, the top advertising company in theworld, will report first-half earnings on Aug. 24, while Havas will do the same after market close on Thursday.
($1 = 0.9088 euros) (Reporting by Mathieu Rosemain and Gwenaelle Barzic, editing byDavid Evans)
