* Issues second sales warning in three months

* Cuts full-year sales growth target to 4 pct, from around 6 pct in August and 6-8 percent previously.

* Q3 sales 4.266 bln eurs vs Reuters poll 4.352 bln euros

* Sees 2008 net earnings per share growth of 7-8 percent at constant exchange rates

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PARIS, Oct 30 (Reuters) - French cosmetics group L'Oreal on Thursday cut its full-year sales forecast for the second time in three months, citing tougher trading conditions, and posted third-quarter sales that came below forecasts. The world's biggest beauty products group said it expected full-year sales growth of 4 percent, down from a previous forecast of around 6 percent at the end of August and 6-8 percent prior to its first sales warning in July.

The Paris-based group, which sells Garnier hair products and Biotherm creams, made sales of 4.266 billion euros ($5.57 billion) in the three months to Sept. 30., up 2.7 percent on a like-for-like basis and 3.4 percent on a reported basis.

The performance compared with expectations of 4.352 billion euros and like-for-like growth of 5 percent based on a Reuters poll of 10 analysts.

L'Oreal, which was previously known in the industry for double-digit earnings per share (EPS) growth, said this year net EPS growth would be in the order of 7-8 percent at constant exchange rates.

The company's sales warning comes after Avon Products , the world's largest direct seller of cosmetics based in the United States, posted a lower than expected quarterly profit this week and Estee Lauder slashed its full-year outlook.

(Reporting by Astrid Wendlandt, Editing by Sudip Kar-Gupta)