Aim: Attention deficit hyperactivity disorder (ADHD ) has been associated with a disturbance in frontal lobe network function, mediated by the underactivity of right hemispheric frontostriatal regions and loss of normal functional asymmetry. The aim of this study was to examine the right hemisphere functions and lateralization of visual-spatial attention in ADHD, using line bisection task. Materials and Methods: Eighteen children with a DSM IV diagnosis of ADHD participated with 18 healthy controls, individually matched for age, sex, handedness and school years. In the line bisection task, horizontal lines were presented on the computer screen. Half of the lines were presented in the right hemispatial area, and half in the left hemispatial area. Participants were instructed to move the vertical cursor to the judged center of the line by mouse. Subjects performed the task separately with each hand. The difference between fine motor performances was examined using finger tapping task. Results: In the line bisection task, bisection performance of the children with ADHD was significantly lower than that of the normal children. For mean bisection error scores, the controls were transecting the lines to the left of the center when the lines were presented in the left hemispace and to the right of the center when the lines were presented in the right hemispace, performing both hands. The subjects with ADHD showed the same but smaller bias than the controls. The apparent deviations from the actual center in the children with ADHD were not significantly different from zero in all conditions. In the finger tapping task, there were no significant differences between two groups for both hands. Conclusion: These results supported the evidence for deficit in visual-spatial attention consistent with disability of the right hemisphere in ADHD.Key words: attention deficit hyperactivity disorder, line bisection task, spatial attention, right cerebral hemisphere Amaç: Dikkat Eksikliği Hiperaktivite Bozukluğu (DEHB)'nun sağ fronto-striatal devreyi ilgilendiren bir bozukluğun sonucu olduğu iddia edilmektedir. Bu çalışmada çizgi bölme testi kullanılarak DEHB'de sağ hemisfer işlevlerinin ve görsel uzaysal dikkatin asimetrisinin incelenmesi amaçlan-mıştır. Gereç ve Yöntem: DSM-IV ölçütlerine göre DEHB tanısı almış, ilaç kullanmayan ve eşlik eden başka nörolojik veya psikiyatrik bozukluğu olmayan 7-14 yaşları arasında sağ elini kullanan 18 çocuk ile onlarla yaş, cinsiyet, el tercihi ve okul yaşı açısından bire bir eşleştirilmiş 18 sağlıklı çocuk araştırmaya dahil edildi. Bütün çocuklar çizgi bölme testini sağ ve sol elleri ile bilgisayar faresi kullanarak yaptılar. Bilgisayar ekranının yatay olarak sağından ve solundan sunulan çizgilerin tam orta noktalarını işaretlemeleri istendi. Ayrıca her iki gruptaki çocukların ince motor yetenekler açısından farkları parmak vuru testi ile değerlendirildi. Bulgular: DEHB olan çocuklar çizgi bölme testinde anlamlı olarak daha çok mutlak hata yaparak kontrol grubuna göre düşük bir performans gösterdi...