Information hiding strategies have recently gained popularity in a variety of fields. Digital audio, video, and images are increasingly being labelled with distinct but undetectable marks that may contain a hidden copyright notice or serial number, or even directly help to prevent unauthorized duplication. This approach is extended to medical images by hiding secret information in them using the structure of a different file format. The hidden information may be related to the patient. In this paper, a method for hiding secret information in DICOM images is proposed based on Discrete Wavelet Transform (DWT). Firstly. segmented all slices of a 3D-image into a specific block size and collecting the host image depend on a generated key, secondly selected the block number and slice number, thirdly, the low-high band used for embedding after adding the generated number, fourthly, used the Hessenberg transform on the blocks that portioned the band (low-high) in a specific size. The secret information (image or text) is a binary value. It was embedded by setting the positive value in the diagonal to odd values if the embedded is one and setting it to even if the secret bit is zero. Several tests were applied, such as applying mean square error, peak signal to noise ratio PSNR, and structural similarity index measure SSIM. Some analyses such as adding noise, scaling, and rotation analysis are applied to test the efficiency. The results of the tests showed the strength of the proposed method.