The court is hearing a complaint from two women, one of whom alleges she was manipulated into handing over 20,000 euros (28,000 dollars) for costly Scientology products, such as an "electrometer" to measure mental energy.
She says she was approached in a Paris street by a Scientologist in late 1998 who offered a free personality test, at a time when she was feeling psychologically fragile.
The plaintiffs' lawyers argue that Scientology resorts to harassment and pressure to rein in victims who show signs of vulnerability.