This BA thesis deals with the issue of unethical acquisition of museum objects, that is, a issue of acquisition that violates the standards and principles set out in ICOM's Code of ethics for museums, mostly the principles under 2.2. Valid title, 2.3. Provenance and Due Diligence, 2.4. Objects and Specimens from Unauthorised or Unscientific Fieldwork. Firstly presented in the thesis is a short description of acquisition of objects and a connection between ethics and museums and later are analyzed and presented examples of instances of unethical acquisitions of objects from the further and closer past, examples that are considered unethical according to the present standards (such as objects acquired during colonization, objects that are war prey etc.) With the examples it is described how museum has handled the fact that the object is unethically acquired, does that museum has the acquisition policy and how is it defined, does museum acknowledges the mistake, does it communicate it to the public and is the object deaccessioned from the collection and returned to those who have the right to it.