Aim. Planning disorders have been observed in people with frontal lobe lesions for many decades. There's also growing body of evidence of frontal dysfunction in people with schizophrenia. The aim of this study is to compare the planning abilities in men with schizophrenia, men with localized frontal lobe lesions and healthy men. Method. A sample of 90 men participated in the study. They were divided into three groups: men with schizophrenia (n=30), men with localized frontal lobe lesions (n=30) and healthy men (n=30) as a control group. Planning abilities were assessed with a clinical trial based on Tower of London task. Results. Significant differences in ToL measures were found between controls and men with schizophrenia (Trials solved: p<0.01; Trials solved perfectly: p<0.05; Execution time: p<0.001) and between controls and men with frontal lobe lesions (Trials solved: p<0.001; Thinking time: p<0.05; Execution time: p<0.001). No significant differences were found between schizophrenia and frontal lobe lesion groups. Conclusions. Similar deficits in planning and solving problems, which require planning, may be observed in men with schizophrenia and men with frontal lobe lesions. In both groups time spent on thinking is less effective than in healthy men. Not only quantitative, but also qualitative assessment should be carried when examining patients' performance on Tower of London task.