Breast cancer has now become the most prevalent malignant tumor in women, and women are becoming more and more concerned about their breasts, and examinations are being done more and more frequently. Breast examinations are mainly color ultrasound, mammogram, and MRI. Ultrasound is simple and easy to perform, there are no rays, and the equipment is easy to purchase, so it can be done from health centers to large hospitals. Mammogram is a more expensive equipment and has only been widely added to major hospitals in recent years. MRI, on the other hand, is less commonly used because of its expensive equipment, time-consuming examination (about 40 minutes) and high examination cost (about 1700 for one side). This article focuses on the choice of ultrasound and mammography. The most common case is that a patient who is only in his 20s comes to the hospital and asks the doctor for a mammogram, thinking that it is the most accurate; or when a patient has a mammogram and the doctor asks for a color ultrasound, the patient will say that he has already had a mammogram and that it is the most accurate, so why do he need another color ultrasound. In fact, these views are wrong. Ultrasound is used to determine the nature of an object based on the echoes of the emitted ultrasound when it meets the object. If the density of the object is high, the reflected echoes will be stronger and appear white on the ultrasound image. Conversely, if the density of the object is low, such as the lowest density of water in the body, the reflected echo will be weak and appear as black on the ultrasound image. (The black part is water, and the white part is glandular, so it is easy to distinguish.) In general, in young women, the breast is mostly dense, so the echoes are stronger on the ultrasound, and the images are mostly white. In middle-aged and older women, the breast gland is gradually degenerating and is slowly being replaced by fat, so the echogenicity is weaker on the ultrasound and the images are mostly black. If there is a lump in the breast, the lump is less dense than the gland, so the echogenicity of the lump is weaker and the image appears black. In this way, a lump in a young woman’s breast appears on the ultrasound as a blackish echogenic mass in a white glandular background, which is easily distinguishable from the other. (See Figure 4, the black part is the lump echo.) In contrast, the lump in middle-aged and older women’s breasts appears as a black lump echo on a black background, which is not obvious and difficult to distinguish. (Because most of the echoes are black, the black echo of the lump is easily ignored.) Therefore, the recognition of breast lumps in young women with breast ultrasound is very high, while middle-aged and elderly women are relatively poor. Moreover, ultrasound can also distinguish whether a lump is cystic or operative, check the boundaries of the lump, and check the blood flow of the lump, which is very valuable for reference, so ultrasound is not necessarily worse than mammogram, but mainly depends on the suitable situation. The mammogram is an image that is formed by receiving rays that pass through the breast. In young women, the breast is dense and the amount of radiation that can penetrate the breast is small, so the mammogram image is mainly white. In middle-aged and older women, the breast is less dense and is mostly replaced by fat, so the mammogram image is predominantly black and the breast lump appears as a white image on the mammogram. Thus, a lump in a young woman’s breast appears as a white lump on a white background, which is poorly recognized and easily ignored. In contrast, in middle-aged and older women, the mammogram image of a lump is a white image of a lump on a black background, which is contrasting and can be easily seen. Therefore, the mammogram is more adaptable for middle-aged and elderly women, and it can reveal calcifications that are difficult to distinguish with ultrasound, and it is more comprehensive and objective, making it an ideal means of screening and medical examination for middle-aged and elderly women. From the above, we can conclude that color ultrasound and mammography have their own advantages and disadvantages due to their different principles, while color ultrasound is more suitable for young women, mammography is more suitable for middle-aged and elderly women, and the combination of the two is more effective. Therefore, young women should not blindly pursue mammography, while middle-aged and older women can undergo mammography if they have the conditions, subject to the doctor’s decision.