* Shares soar 59 pct in debut

* Strongest debut since November 2007

* 7th straight IPO with first day pop (Updates with closing price, IPO details)

By Phil Wahba

NEW YORK, May 21 (Reuters) - Shares of OpenTable Inc (OPEN.O: Quote, Profile, Research) closed their first trading session up 59 percent on Thursday following the restaurant reservation company's initial public offering, in the best first day performance for a U.S. company in over 18 months.

The stock ended up $11.89 at $31.85 on Nasdaq, a day after the company raised a more-than-expected $60 million in its IPO. The gains were in contrast to the 1.89 percent decline of the wider Nasdaq Composite Index .IXIC.

The stock started trading at a 22.5 percent premium over the $20 IPO price, which was above the expected range, reaching an intraday high of $35.50.

"It's such a small deal and people are interested in the brand name, plus it's the first real VC (venture capital)-backed IPO by a Silicon Valley firm in a while," said Nick Einhorn, an analyst with Connecticut-based Renaissance Capital.

OpenTable sold a modest 3 million shares, something Einhorn said will make the stock more volatile and could explain its strong debut.