Shares of online and mobile food delivery and ordering company GrubHub (GRUB) are falling despite the company's report of solid quarterly financial performance as growth in its "active diners" slows.

WHAT'S NEW: The company, whose shares are up about 60% year-to-date, including today's decline, reported third quarter earnings per share of 23c on revenue of $123.5M. Analysts were expecting EPS of 19c on revenue of $118.45M. "We are pleased with Grubhub's third quarter growth, as we continue building the most comprehensive marketplace for restaurants and takeout diners. Our product improvements and investment in delivery continue to generate high levels of sustainable growth," said Matt Maloney, GrubHub CEO. "GrubHub is now delivering for restaurant partners in over 60 markets nationwide, and our growth rate is generally highest in markets where a substantial percentage of orders are being delivered by our drivers." For the current quarter, the company predicts revenue of 136M-$138M, against analysts' consensus estimate of $136.18M.

ACTIVE DINER GROWTH SLOWS: Along with its quarterly earnings report, GrubHub noted that active diners were 7.69M a 19% year-over-year increase from the same quarter of last year, but slower than the 24% year-over-year increase in active diners that the company reported in Q2.

PRICE ACTION: GrubHub is down 11.5%, or $4.99 per share, in afternoon trading to $38.40 per share.