Unless it says, "Made from Real Wasabi Horseradish" then it is not made from real wasabi horseradish.
Wasabi = Botanical/Scientific/Latin name of plant:
Wasabia japonicaHorseradish = Botanical/Scientific/Latin name of plant:
Armoracia rusticana
They are not the same plant, however (sorry Mangilao30) they are from the same plant family: Brassicaceae (cabbage family).
The real wasabi plant is difficult to grow. Therefore making mass production inefficient and unprofitable. This is why wasabi powder is made from the more common horseradish (
Armoracia rusticana).
If you want to try real wasabi, look for it in tube form. I've purchased it at grocery stores. Or you can order it here:
http://www.afcsushi.com/sushirelProd/sushimak.html
If you're ambitious, you can try growing real wasabi yourself for a ready supply:
Growing real wasabi