Wozniacki lost nearly two-thirds of the points in the first set before pulling her game together for a 1-6, 6-2, 6-3 victory over the seventh-seeded Dementieva.
It was Wozniacki's 11th WTA title -- fifth this year -- and put her in position to move to the world No. 1 ranking if she advances as far as the quarterfinals of next week's tournament in Beijing.
"Elena started really strong. I didn't get enough depth on my groundstrokes, but in the beginning of the second set I pressed a little harder," Wozniacki said. "I started to feel the match was turning around a little bit, but I still had to keep my focus in the third set and I'm just happy I won the last point."
Dementieva dropped only four points on serve in the first set but had her serve broken five times over the last two sets. Wozniacki won 58 percent of the points in the second and third sets and nearly half of those on Dementieva's serve.
Wozniacki took the first-place check for $350,000 and pushed her 2010 winnings to nearly $2.5 million. Dementieva collected $175,000 as the Pan Pacific runner-up.