Viacom reported a 7 percent rise in its first-quarter operating profits in spite of poor performance by its radio and television divisions, as its cable networks showed strong growth.

This sent Viacom’s shares up 2.7 percent, or 94 cents, to $34.90 in mid-day trading in New York on Tuesday.

Viacom’s overall earnings in the first quarter of 2005 were $585 million, or 36 cents per share.

The operating income of its television division, which includes the broadcast networks CBS and UPN, dropped 8 percent to $304 million, and its radio division saw a 5 percent drop in its operating income, to $189 million.

However, Viacom’s cable group, which includes MTV and Nickelodeon, scored a 19 percent gain in revenues and a 20 percent rise in its operating income.

This report seems to justify Viacom’s previously announced intention to split into two separate groups, along cable/broadcast lines, a split that could happen as early as the first quarter of 2006.

Viacom’s first-quarter earnings for 2005 actually dropped 18 percent from the same period in 2004, but that quarter’s earnings were enhanced by a $111 million tax benefit.