Electronics retailer RadioShack Corp. on Thursday posted a better-than-expected second-quarter profit, even as its profit fell nearly 12 percent. Its shares climbed nearly 17 percent in midday trading.

Profit declined to $41.4 million, or 32 cents per share, in the three months ended June 30 from a year-ago profit of $47 million, or 34 cents per share, when a tax-related gain lifted results.

Sales rose about 6 percent to $994.9 million from $934.8 million.

A year ago, a $10 million reversal of an income tax contingency reserve boosted profit, while results in the most recent quarter were hurt by a one-time charge of $4.3 million to amend its corporate headquarters lease.

Adjusting for these items, profit rose to 35 cents per share from 27 cents per share a year earlier.

Analysts polled by Thomson Financial, who typically exclude one-time items from their estimates, expected profit of 26 cents per share and sales of $908.5 million.

"Although we sensed that sales were getting modestly better (a principal reason for our upgrade several weeks back), we did not expect such a sharp improvement in the quarter," RBC Capital Markets analyst Scot Ciccarelli wrote in a research note Thursday.

Same-store sales rose 6.9 percent because of strong sales of items that include, among others, global positioning system devices and prepaid wireless phones.

Same-store sales are sales at stores open at least a year, and are a key indicator of retailer performance since it measures growth at existing stores rather than newly opened ones.

The company also said it posted improvement in its AT&T post-paid business, but warned that its Sprint post-paid business "continues to be a significant negative impact" on RadioShack's performance.

"The economic environment continues to be challenging, however, as a credit to our tream, we are pleased with our progress as we begin to drive profitable growth," Chief Executive Julian Day said in a statement.