The subject of this work is to study the use of object oriented models of petrochemical plants in order to si mplify simulation and production planning. A prototype system for an existing plant was developed to achieve this goal. The prototype system was made using the object oriented programming language Smalltalk/V. The system is generic and allows creating graphical simulation models for most kinds of petrochemical plants main ly as a simple drawing operation. The models can be used for simulating production plans as well as for generating them automatically. The results obtained prove that object ori ented methods allow the creation of very flexible models. These models are shown to facilitate simulation and automatic scheduling, when used together with artificial intelligence methods.