Boston area housing values increased by 2.4 percent in May compared with April, according to data released Tuesday by the S&P/Case-Shiller Home Price Indices.

That marked the second consecutive month of increasing values in the region following eight months of slight declines, according to the index. S&P/Case Shiller is considered by real estate specialists to be one of the most accurate measures of home values because it’s based on repeat sales of properties.

The May increase helped boost values in the Boston area year-over-year, leaving home prices largely flat compared with 2011, according to the index. Home prices dropped by just 0.1 percent in May compared with the same period last year, Case-Shiller reported.

But home prices in the Boston area did not drop as dramatically as they did in many other metro areas during the housing collapse. Overall, values here are now down about 17 percent from their peak in the fall of 2005, according to the index. By contrast, prices in the Phoenix region are still down by more than 50 percent from their apex six years ago. Nationwide, home values increased an average of 2.2 percent in May, Case-Shiller said. The largest monthly gains were recorded in Atlanta, Chicago, and San Francisco.

Despite the monthly gains, home prices across the United States are still declining by an annualized rate of 0.7 percent, and home values are down nearly 33 percent since the housing peak. The index tracks 20 metro areas.

David M. Blitzer, chair of the Index Committee at S&P Dow Jones Indices, said the rising values are a positive sign, tempered by the fact that property values generally increase during the spring months. “The housing market seems to be stabilizing, but we are definitely in a wait-and-see mode for the next few months,” Blitzer said.