Dehydration of carrot (Daucus carota L.) is a method of preservation to make it available throughout the year. An investigation was carried out to study effects of hot air and freeze-drying on bioactive compounds and antioxidant activity in carrot slices. Carrot slices were pretreated with potassium metabisulphite (KMS) prior to drying. Hot-air drying of carrot slices was at 60 ± 5 °C; freeze-drying was at −30 °C. Dried carrot slices were analyzed for antioxidant activity by DPPH assay on the bioactive compounds total carotenoids, β-carotene, total phenolics, tannins, ascorbic acid and lycopene. Freeze-drying better retained antioxidant activity and bioactive compounds in carrot slices compared with hot-air drying. Sulphur dioxide in KMS, an antioxidative, beneficially affected retention of bioactive compounds during hot-air drying, but had negligible effects during freeze-drying. The rehydration ratio was higher in freeze-dried carrot slices compared with hot-air-dried carrot slices. During storage minimum loss occurred for KMS treated hot-air-dried carrot slices then by KMS treated freeze-dried, control freeze-dried and control hot-air-dried carrot slices. Sulphur dioxide as a pretreatment prior to hot-air drying beneficially retained bioactive compounds in carrot slices compared with freeze-drying.