diff --git a/service/create_order.go b/service/create_order.go
index f5b1a80..297af43 100644
--- a/service/create_order.go
+++ b/service/create_order.go
@@ -58,6 +58,16 @@ func (s *Service) createNewOrder(ctx context.Context, input CreateOrderInput, us
 
 	logctx.Debug(ctx, "creating new order", logger.String("orderId", orderId.String()), logger.String("clientOrderId", input.ClientOrderID.String()))
 
+	if input.Price.IsZero() || input.Price.IsNegative() {
+		logctx.Warn(ctx, "price has to be positive", logger.String("orderId", orderId.String()), logger.String("price", input.Price.String()))
+		return models.Order{}, models.ErrInvalidInput
+	}
+
+	if input.Size.IsZero() || input.Size.IsNegative() {
+		logctx.Warn(ctx, "size has to be positive", logger.String("orderId", orderId.String()), logger.String("size", input.Size.String()))
+		return models.Order{}, models.ErrInvalidInput
+	}
+
 	order := models.Order{
 		Id:        orderId,
 		ClientOId: input.ClientOrderID,
diff --git a/transport/rest/create_order.go b/transport/rest/create_order.go
index 1453d3b..11f5804 100644
--- a/transport/rest/create_order.go
+++ b/transport/rest/create_order.go
@@ -190,7 +190,7 @@ func parseFields(_ http.ResponseWriter, input pFInput) (*pfParsed, error) {
 		return nil, fmt.Errorf("'price' is not a valid number format")
 	}
 
-	if decPrice.IsNegative() {
+	if decPrice.IsZero() || decPrice.IsNegative() {
 		return nil, fmt.Errorf("'price' must be positive")
 	}
 
@@ -205,7 +205,7 @@ func parseFields(_ http.ResponseWriter, input pFInput) (*pfParsed, error) {
 		return nil, fmt.Errorf("'size' is not a valid number format")
 	}
 
-	if decSize.IsNegative() {
+	if decSize.IsZero() || decSize.IsNegative() {
 		return nil, fmt.Errorf("'size' must be positive")
 	}