New York - Christos M. Cotsakos, the flamboyant chairman of the E*Trade Group whose huge pay packages have angered investors, resigned suddenly last Friday.

E*Trade, the online brokerage firm, said the departure of Cotsakos, who gave back part of an $80 million compensation package last summer, was a mutual decision made by him and the company’s directors. Mitchell H. Caplan, the company’s president, will succeed Cotsakos as chief executive. A director, George Hayter, will become the board’s non-executive chairman.

“There’s never a right time or a good time,” he said. “There’s just a moment. This was the right time to do something different.”

Cotsakos, 54 said he planned to write books, teach children and become involved with “entrepreneurial start-ups.”

E*Trade, based in Menlo Park, Calif., has had some success in branching out from stock trading into online banking. But its stock price has languished, some analysts said, because investors remained concerned about how Cotsakos was running the company.

“From an investor’s standpoint, this removes one big source of controversy,” said Ken Smith, co-manager of the Munder-NetNet fund, which owns about six million shares of E*Trade. “He got paid a lot of money and, to some degree, he probably deserved it. He took a real small company and made it into a household name.”

Smith said the change in command did not alter his opinion of the company’s prospects because he did not expect any change in operations. But, he said, the stock could rise on the news because “this takes away something that might have caused other investors to not look at it.”

In trading on the New York Stock Exchange yesterday, E*Trade’s shares were unchanged at $4.49, down 93 percent from their high in April 1999.

Richard H. Repetto, an analyst at Putnam Lovell NBF in New York, lowered his estimate of the stock’s fair value to $6 from $7 to $8 this week, after the company gave a measured outlook for the coming year. But he said he expected the executive change to give the stock a lift.

“Investors were concerned about governance,” Repetto said. “The stock has traded at a discount to its peers. I attributed the discount to a number of factors, not the least of which was corporate governance.”

Flush with commissions paid by individual investors during the stock trading frenzy of the late 1990’s, Cotsakos went on a spending spree. He appeared with a chimpanzee in ads that ran during the 2002 Super Bowl, the most expensive commercial time on television.

E*Trade also sponsored the half-time show at the Super Bowl for three years, before dropping its sponsorship this year. Lately, it has been sponsoring the Rolling Stones’ concert tour. The company also opened flashy stores in high-rent districts, including one on Madison Avenue in Midtown Manhattan.

For years, Cotsakos traveled frequently to London in pursuit of a doctorate from the London School of Economics. He completed the degree last year. Under fire from investors for his pay, Cotsakos agreed last year to forfeit $21 million of the $80 million the company had agreed to pay him for 2001.

The company also received criticism for its practice of lending large sums to its executives to buy homes in Silicon Valley at the height of the housing market there. All of those loans have been repaid and the company will make no more, Cotsakos said.

Caplan, 45, is succeeding Cotsakos on the board, too. He declined to say how much he would be paid, but said that his compensation would be determined by a committee of independent directors and would be “in alignment” with that of his peers. Caplan, a more staid executive who has overseen E*Trade’s push into electronic banking, said the company remained committed to providing online brokerage services.

Cotsakos predicted that his detractors would be proved wrong eventually.

“If you build the right franchise, the stock price will always follow,” he said. “That will bear things out over time.”