The aim of this study was to determine whether the baseline oral health-related behaviors of the participants of the intervention group of a randomized clinical trial conducted in Pori, Finland, were predictive of failures in controlling caries. Three definitions of failure were considered, namely if the children developed one or more, three or more, or five or more new caries lesions, as evidenced by the change in number of decayed, missing or filled surfaces (Δ DMFS) during the follow-up period of 3.4 yr. Children (n = 497) aged 11–12 yr, with at least one active initial caries lesion at baseline, were studied. The data were based on clinical examinations in 2001 and 2005 and on a questionnaire on oral health-related behaviors that was administered in 2001. Associations between baseline behaviors and the measures of failure in caries control were evaluated using logistic regression analyses. Self-reported tooth brushing with fluoride toothpaste at least twice a day reduced the risk of failure. Children who, at baseline, reported eating candy at least once a day were more likely to experience failure at the levels of three or more and five or more new lesions.