Wall Street analysts proved once again that they are a tough crowd to please.

Following the release of strong first-quarter results, shares in Comcast stalled last week as analysts found plenty of reasons to jeer, rather than cheer, the cable giant’s numbers.

Despite Comcast’s nearly quadrupling its first-quarter profit and recording strong gains in the number of customers signing up for high-speed data services or digital video recorders, several Wall Street researchers groused that the company’s results, while robust, masked some challenges that could trip up growth.

Specifically, analysts are worried about a larger-than-expected decline in basic cable subscribers, while others fretted over whether the company is relying too much on discounting to fuel its high-speed data growth.

If persistent, both factors could loom large as Comcast faces stiffer competition from satellite operators that have already snagged disaffected cable subscribers and from telephone companies, which are offering deep discounts for their high-speed data product and are set to offer video services later this year.

To be sure, the company’s first-quarter results showed that Comcast still has plenty of strength. Last Thursday it reported a 382 percent surge in first-quarter profit to $313 million, compared with a year-ago profit of $65 million. Revenue rose 9 percent to $5.4 billion.

Much of the growth was a result of robust sales of digital-cable products such as digital video recorders and video-on-demand services, both of which helped generate 200,000 new digital-cable subscribers as well as the addition of 414,000 high-speed data customers. Those factors helped the cable division report a 10 percent increase in revenue to $5.1 billion.

Meanwhile, Comcast’s content business also posted gains during the period, with revenue surging 21 percent to $213 million, driven mainly by strong results at the Golf Channel that more than offset higher expenses associated with Comcast’s newer cable channels.

But Richard Greenfield, a media analyst at Fulcrum Global Partners, noted that half of Comcast’s overall first-quarter revenue growth was fueled by the company’s high-speed data product, which is being heavily promoted with discounted pricing of $19.99 a month for the first six months plus $50 cash back. He predicted that the marketplace could see more of these kinds of promotions as cable operators begin to lose market share to the telephone company’s digital subscriber lines.

“The big question is whether data discounting will begin to diminish data growth, which has been the key driver” behind the company’s revenue and cash flow gains, he said.

Analysts were also taken aback by the basic cable subscriber loss in the quarter, which totaled 29,000 and flew in the face of predictions of subscriber gains in the period. A number of observers noted that such results indicate that satellite operators are continuing to lure away subscribers at a time when the fight for customers is likely to grow fiercer with the arrival of the video product from telephone companies.

However, analysts said that Comcast has bright spots, in particular the rollout of its cable-based phone service. The company provided more details of its deployment strategy, saying it planned to introduce the service in Hartford, Conn., and Boston within the next 30 days and then Chicago and Portland, Ore., within the next 60 days.