Spinal anesthesia is widely used in different patient positions to create efficient and rapid anesthesia induction in surgical interventions. Early and late complications of spinal anesthesia may vary according to the type of needle, drug dose and concentration, patient weight and height, puncture technique, and position of the patient. This study aimed to prospectively compare early complications of spinal anesthesia between patients in sitting and lateral decubitus positions with motor block onset time and sensory block time to T10 level. Spinal anesthesia was performed in 100 ASA I-II patients aged 18-65 years (group S=48; and group L=52) undergoing arthroscopic knee surgery. Hemodynamic data, early complications, sensory and motor block onset times were recorded. Systolic, diastolic and mean arterial pressures were significantly lower in lateral decubitus position as compared to sitting position after spinal anesthesia induction. Arterial blood pressure values decreased significantly in lateral decubitus position as compared with sitting position. Motor block onset time and sensory block onset time were shorter in lateral decubitus position than in sitting position. Accordingly, sitting position could be suggested during induction of spinal anesthesia because it was associated with less pronounced decrease in blood pressures.