* Q4 EPS $0.18 vs est $0.13/shr * Q4 revenue up 34 pct

* Sees Q1 EPS $0.03-$0.08 vs est $0.09/shr

* Says difficult to provide outlook beyond Q1 * Shares down 13 pct (Adds comments from conference call)

June 11 (Reuters) - ArcSight Inc (ARST.O: Quote, Profile, Research), a provider of security and compliance management software, posted a quarterly profit that topped market estimates, helped by higher product revenue, but forecast a weak first quarter, sending its shares down 13 percent.

The company said the forecast was based on current business trends and anticipated seasonally lower first quarter.

In a conference call with analysts, ArcSight said it would make significant investments in IT infrastructure in 2010, driving an increase in operating costs and capital expenditure during the period.

The difficult economic environment makes it tough to provide reliable forecast beyond the first quarter, it said on the call.

For the fourth quarter, the company reported earnings of $4.3 million, or 13 cents a share, compared with a loss of $1.1 million, or 4 cents a share, a year ago.

Excluding items, it earned 18 cents a share. Revenue rose 34 percent to $39.3 million, mainly on a 31 percent jump in product revenue.