The newspaper said it did an analysis of three years of data for suburban law enforcement departments and found that just 44 percent of searches triggered by dog alerts turned up drugs or drug paraphernalia.
The report said for Hispanic drivers the rate drops to 27 percent.
Not finding drugs doesn't mean there weren't drugs present at some time, proponents of drug-sniffing dogs said.
Officer and dog training are important to the success of the program, dog-trainer Alex Rothacker said.
"If you don't train, you can't be confident in your dog," said Rothacker, who works with dozens of drug-sniffing dogs. "A lot of dogs don't train. A lot of dogs aren't good."
Some critics argue officers with drug-sniffing dogs target minorities.
"We know that there is a level of racial profiling going on, and this is just another indicator of that," said Virginia Martinez, a Chicago-based staff attorney for the Mexican American Legal Defense and Educational Fund.
Complicating the drug-sniffing dog scenario is the lack of a system of standards or certification for officer-dog teams, critics said.
A federally sponsored advisory commission developed a recommended set of best practices but they're not backed by any legal mandate.