Layered perovskite-like oxides are known as promising materials for electronics, chemical technology, environment. Using of these compounds in different areas of application depends on their thermal and chemical stability. Due to particularities of structure layered oxides are favorable to topochemical processes which happen without significant change of structure. These reactions could be in different medium (in water suspension, in melt, in gas atmosphere) at room temperature or heating. Topochemical reactions impacts on chemical stability and also they are the way of the synthesis of new compounds and materials on their base by means of low temperature reactions. In some cases there is a great influence of topochemical processes on functional properties of materials as photocatalytic activity [1]. Here in it will be reported the spectrum of topochemical reactions which are typical for layered perovskite-like oxides. Opportunities and advantages of thermochemical investigations of topochemical processes as a main method in complex research combined different physical methods as XRD, SEM, FTIR, NMR will be demonstrated. Objects under investigation include structures with different thickness of perovskite blocks (mono-layered, double-layered, triple-layered), with different cationic content of perovskite layers (titanates, tantalates, niobates) and different cations (alkali, earth-alkali, rare-earth) occupied the interlayer space. Results of thermochemical investigation (thermogravimetry, differential scanning calorimetry, simultaneous thermal analysis coupled with mass-spectrometric evolved gas analysis,water sorption analysis) will be present for following reactions: ion-exchange, intercalation, deintercalation, protonation, dehydration [2-5]. Content of intermediates and products, overall reaction heat effects and effects of different stages combined with structural data have been used for the description of topochemical processes in layered oxides.