Cablevision lost 16,000 basic subscribers during the third quarter, following subscriber losses in the preceding quarter, as it faced mounting competition from Verizon Communications and satellite TV operators in its region.
Oppenheimer had forecast the operator would lose 10,000 subscribers.
Cablevision said it added 35,000 digital video subscribers and 52,000 new high speed Internet subscribers. Oppenheimer expected 44,000 digital video additions and 41,000 Internet additions.
It also added another 91,000 phone subscribers compared with the Oppenheimer forecast of 66,000.
Cablevision lowered its outlook for the number of services it would sell in 2007 to 800,000 units down from a previous estimate of 825,000 to 900,000.
"The customer numbers were mixed and they reduced guidance, so we'd say their results were lackluster," said Thomas Eagan, analyst at Oppenheimer.
Cablevision said its third-quarter net loss widened to $79.3 million, or 27 cents a share compared with a net loss of $59.2 million or 22 cents per share a year earlier. Prior-year results included a tax benefit.
Revenue rose 9.4 percent to $1.512 billion.
Wall Street analysts on average expected Cablevision to post revenue of $1.545 billion, according to Reuters Estimates.
Last month, Cablevision shareholders rejected a $10.6 billion buyout bid offered by the Dolan family, after major stakeowners said it undervalued the business.
Cablevision, which has 3 million cable TV subscribers in the New York area, owns several cable networks as well as major sports teams and venues including Radio City Music Hall, Madison Square Garden, the New York Knicks basketball team and the New York Rangers ice hockey team.
Shares of Cablevision were down 66 cents at $25.87 on the New York Stock Exchange after falling as low as $25.57.