Introduction.　User-contributed　information　on　health-related　social　media　sites　contains　useful　user-experience　information　that　complements　information　on　authoritative　health　information　websites.　Though　more　people　are　searching　and　browsing　social　media　sites　for　health　information,　there　are　few　studies　of　user　browsing　behaviour　on　these　sites,　and　the　factors　that　affect　the　behaviour.　This　study　investigated　the　factors　affecting　the　users＇　skimming　and　examining　durations　when　browsing　a　health　discussion　forum.　Methods.　An　eye-tracker　system　was　used　to　record　users＇　eye　fixations　and　eye　movements　when　browsing　a　health　discussion　forum,　HealthBoards.com.　Analysis.　Stepwise　multiple　linear　re　gression　was　used　to　develop　models　to　predict　users＇　skimming　and　examining　durations.　Results.　The　type　of　health　information　need　context　(i.e.　browsing　for　own　health　issue,　browsing　for　someone　else＇s　health　issue,　and　browsing　with　no　particular　health　issue　in　mind),　the　perceived　urgency　of　the　health　information　need,　and　the　length　of　the　health　information　text　were　found　to　be　significant　predictors　of　the　examining　and　skimming　durations.　Demographic　factors　of　gender　and　age　were　not　significant.　Conclusion　Future　studies　of　online　health　information　seeking　should　take　these　three　factors　into　consideration,　and　distinguish　between　browsing　two　types　of　screens-the　summary　screen　of　document　surrogates　and　the　detailed　content　screen.