In Alternext, companies could choose two different kinds of IPO mechanisms; one is Public Offer, and the other is Private Placement. In fact, Private Placement in Alternext means 100% book-building. This article focused on what kind of companies would intend to choose Private Placement other than Public Offer, and compared their IPO discounts and market performance with companies using another mechanism. Companies with low profitability and no family holding would prefer to use Private Placement. However, companies with highly information asymmetry and profitability would also choose Private Placement. From the view of post-IPO liquidity, we infer that companies that choose Private Placement may be due to their preference for long-term investors. Referring to IPO indirect cost, we found that companies choosing Private Placement pay higher IPO discount cost. However, their post-IPO cumulated abnormal returns (CAR) are higher than companies using Public Offering.