This study was aimed to investigate the possibility of using C-reactive protein (CRP) as a marker for 11 types of cancer include (Ovarian, Bone, Pancreas, Liver, Lung, Cervical, Head, Kidney, Breast, Stomach and Prostate cancer) and poising thyroid gland disease by qualitative test for CRP. 50 serum samples from health human and about 150 serum samples were examined from patients with cancer and poising thyroid gland disease (aged between 14 and 85 years old). Qualitative test was done to detect the presence of CRP in the patient’s serum. The qualitative test showed that all normal samples 50 (100%) give negative result for the presence of CRP in the serum. While 116 (89.9%) patients give negative result and 13 (10.1%) patients with cancer diseases give positive result to presence of CRP in the serum. And also 21 (100%) patients with poising thyroid gland disease give positive result to CRP. According to the results of this study C-reactive protein consider non-specific marker for all types of cancer diseases but can be used as marker for bone cancer. On the other hand CRP which demonstrated that, it a useful marker for patients with poising thyroid gland.