Among the children we treat with school phobia, some of them have co-morbid bipolar disorder, which can make clinical diagnosis difficult. Because school phobia symptoms are often more obvious and easy to draw attention to, this often masks the symptoms of co-existing bipolar disorder, leading to underdiagnosis. School phobia is a disorder of an anxiety nature, and anxiety disorders tend to be fearful of death, so school phobic children are usually not at risk of suicide. However, bipolar depression in bipolar disorder has the highest suicide risk of any mental illness, higher than major depression alone. So, if school phobia co-morbidly affects bipolar disorder, and bipolar disorder is under-diagnosed, there is a risk of accidents in treatment. Therefore, clinicians, and also counselors in counseling facilities, should pay special attention to the presence of co-occurring bipolar disorder when treating a child with school phobia. Another reason for under-diagnosis is that the co-existence of school phobia leads to atypical symptoms of bipolar disorder, e.g., anxious depression in the case of depression and agitated mania in the case of mania. Since school phobic children are often sensitive, suspicious and socially fearful, when co-morbid with bipolar disorder, their general clinical presentation sometimes looks like schizophrenia, which can be easily misdiagnosed as schizophrenia if the doctor fails to understand the condition in depth.