To investigate the loneliness of female juvenile delinquents through quantitative and qualitative data. For quantitative data, participants were 100 juvenile delinquents in Girl Training Center: Ban Prani. The instruments used were the Loneliness Scale and the Family Functioning Scale. Data was analyzed using the one-way and two-way ANOVA designs followed by post-hoc multiple comparisons with Dunnett's T3 test, and the Pearson correlation coefficient. The qualitative data was obtained through indepth interview with 11 girls, drawn from the 100 juvenile delinquents of the quantitative part, who reported high and relatively high loneliness. The major findings were 1) Female juvenile delinquents reported relatively low level of loneliness and relatively high level of family functioning. 2) The juvenile delinquents with relatively high and low level of family functioning reported more loneliness than those with high level of family functioning. 3) The juvenile delinquents whose families moved to reside in Bangkok reported more loneliness than those who resided in Bangkok. 4) The juvenile delinquents with suicidal intentions reported more loneliness than those with no suicidal intentions. 5) No significant effects for age level, academic level, marital status, type and number of perpretation family background and parents' vocation on juvenile delinquents' loneliness were found. 6) Loneliness and family functioning were negatively related. 7) The female juvenile delinquents with high and relatively high level of loneliness tended to present negative patterns of affective, cognitive, and behavioral characteristics. Experienced sufferings, lonely feelings, inpatient boredom, lack of significant relationships, self-pitiness, negative self and other evaluation, and social isolation were reported. Some reported experienced anxiety, emptiness, social failure, lack of affection and understanding, and lack of autonomy. In coping with loneliness, the participants reported more use of relaxation, seeking to belong, keep problems to self, not coping; and were less likely to seek social support
