The features of paper are considered in comparison with traditional substrates used in flexible electronics. Analysis of the research results shows that paper substrates cannot replace plastic substrates and silicon in all applications. But in specific applications, paper substrates can certainly be used as a viable alternative to traditional materials. It has been shown that paper has a number of advantages that make it very promising for use in the development of various elements of flexible biodegradable electronics, such as optoelectrochemical, electrochemical sensors, gas and humidity sensors, microfluidic analytical devices, physical sensors, green and wearable electronics, and optoelectronics. At the same time, it is indicated that paper also has disadvantages that may limit its widespread use, and therefore, they need to be eliminated.