Citrus oils are a complex mixture of more than a hundred components of differing chemical natures. The study of the physiologically active components of citrics and their contribution to human health is a growing research field. The aim of this work was to determine the chemical composition of four citrus oils: mandarin (C. reticulata L.), grapefruit (C. paradisi L.), lemon (C. limon L.), and orange (C. sinensis L.). The oils were chemically analysed and identified by Gas chromatography mass spectrometry (GC-MS). The principal components of the essential oils were as follows. Mandarin: limonene (74.7 %) and λ-terpinene (15.7 %); lemon: limonene (69.9 %) and β-pinene (11.2 %); orange: limonene (94.9 %) and β-myrcene (1.16 %); grapefruit: limonene (96.2 %) and myrcene (1.4 %). In all four analysed citrus oils limonene was the most abundant component. The great variability may have been due to several factors, among them the particular varieties studied, the geographical location, season and environmental factors, such as soil type and climate, genetic factors processing and extraction method and the part of the plant used to extract the oil.